Biodegradable polyester resin composition and biodegradable polyester molded article including the same

ABSTRACT

An eco-friendly biodegradable polyester resin composition includes: a polyester resin including a diol, an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid; and 5000 ppm to 20000 ppm of a hydrophilic regulator having a molecular weight of 400 to 1300.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean PatentApplication Nos. 10-2022-0062443, filed on May 21, 2022, and10-2022-0062447, filed on May 21, 2022, the disclosure of which isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

Embodiments relate to a biodegradable polyester resin composition, abiodegradable polyester film including the same and a biodegradablemolded article including the biodegradable polyester resin composition.

2. Description of Related Art

Recently, a solution to the problem of handling various household items,especially disposable products, is required as concerns aboutenvironmental problems increase. Specifically, polymeric materials areinexpensive and have excellent processability properties, so they arewidely used to manufacture various products such as films, fibers,packaging materials, bottles, containers, etc. However, polymermaterials have the disadvantage that harmful substances are emitted whenincinerated when the lifespan of a product is over, and it takeshundreds of years depending on the types thereof to completely decomposethem naturally.

To overcome the limitations of the polymers, research on biodegradablepolymers that are decomposed within a short period of time is beingactively conducted. As biodegradable polymers, polylactic acid (PLA),polybutyleneadipate terephthalate (PBAT), polybutylene succinate (PBS),and the like are being used.

Such biodegradable resin compositions are disclosed in Korean PatentApplication No. 2012-0103158, and the like.

SUMMARY OF THE INVENTION

Therefore, the present disclosure has been made in view of the aboveproblems, and it is an object of the present disclosure to provide abiodegradable polyester resin composition having a high hydrolysisdegree not only in soil but also in water when discarded while having anadequate initial hydrolysis degree and appropriate biodegradability; anda biodegradable polyester film including the same.

In accordance with an aspect of the present disclosure, the above andother objects can be accomplished by the provision of a biodegradablepolyester resin composition, including: a polyester resin including adiol, an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid;and 5000 ppm to 20000 ppm of a hydrophilic regulator having a molecularweight of 400 to 1300.

In an embodiment, the hydrophilic regulator may include an oligomerformed by reaction of at least two of the diol, the aromaticdicarboxylic acid and the aliphatic dicarboxylic acid.

In the biodegradable polyester resin composition according to anembodiment, a hydrolysis degree after one week may be 35% to 60%, and ahydrolysis degree after three weeks may be 85% or more, wherein thehydrolysis degree after one week and the hydrolysis degree after threeweeks are measured by a measurement method described below:

[Measurement Method]

The hydrolysis degree after one week is a number average molecularweight reduction rate, compared to an initial number average molecularweight of the biodegradable polyester film, of the biodegradablepolyester film placed for one week under high-temperature andhigh-humidity conditions of 80° C. and a relative humidity of 100%, andthe hydrolysis degree after three weeks is a number average molecularweight reduction rate, compared to an initial number average molecularweight of the biodegradable polyester film, of the biodegradablepolyester film placed for three weeks under high-temperature andhigh-humidity conditions of 80° C. and a relative humidity of 100%.

In an embodiment, the hydrophilic regulator may include: a firstoligomer having a molecular weight of 415 to 425; a second oligomerhaving a molecular weight of 620 to 630; a third oligomer having amolecular weight of 640 to 650; and a fourth oligomer having a molecularweight of 840 to 850.

In an embodiment, a content of the first oligomer range from 3000 to5000 ppm based on the polyester resin, a content of the second oligomerrange from 2000 ppm to 4000 ppm based on the polyester resin, a contentof the third oligomer range from 500 ppm to 2000 ppm based on thepolyester resin, and a content of the fourth oligomer range from 700 ppmto 2500p ppm based on the polyester resin.

In an embodiment, the hydrophilic regulator may include a firstoligomer, wherein the first oligomer includes one first unit representedby Formula 6 below and one second unit represented by Formula 7 below:

In an embodiment, the hydrophilic regulator may include a secondoligomer; and a third oligomer, wherein the second oligomer includes onefirst unit denoted above and two second units denoted above, the thirdoligomer includes two first units denoted above and one second unitdenoted above, and the second oligomer is included in the hydrophilicregulator in a higher content than the third oligomer.

In an embodiment, the hydrophilic regulator may further include a fourtholigomer, wherein the fourth oligomer includes two first units denotedabove and two second units denoted above.

In the biodegradable polyester resin composition according to anembodiment, a water contact angle of the biodegradable polyester resincomposition measured by a measurement method below may be 65° to 90°,and a polarity of the biodegradable polyester resin composition measuredby a measurement method described below is 4 mN/m to 7 mN/m:

[Measurement Method]

The biodegradable polyester resin composition is dried at 80° C., placedin a stainless steel mold, and compressed at 210° C. under a pressure of10 MPa for 3 minutes to produce a polyester sheet having a thickness of300 μm, and the water contact angle and the polarity are measured on asurface of the polyester sheet.

In the biodegradable polyester resin composition according to anembodiment, a biodegradability of the biodegradable polyester resincomposition after one week may be 45% to 65%, a biodegradability of thebiodegradable polyester resin composition after nine weeks may be 85% ormore, wherein the biodegradability after one week and thebiodegradability after nine weeks are measured by a measurement methoddescribed below:

[Measurement Method]

The biodegradability after one week is a molecular weight reductionrate, compared to an initial molecular weight of the biodegradablepolyester resin composition, of the biodegradable polyester resincomposition placed at 60° C. and a relative humidity of 90% for one weekunder composting conditions, and the biodegradability after nine weeksis a molecular weight reduction rate, compared to an initial molecularweight of the biodegradable polyester resin composition, of thebiodegradable polyester resin composition placed at 60° C. and arelative humidity of 90% for nine weeks under composting conditions.

In accordance with another aspect of the present disclosure, there isprovided a biodegradable polyester resin composition, including apolyester resin including a diol, an aromatic dicarboxylic acid and analiphatic dicarboxylic acid, a hydrolysis degree after one week is 35%to 60%, and a hydrolysis degree after three weeks is 85% or more,wherein the hydrolysis degree after one week and the hydrolysis degreeafter three weeks are measured by a measurement method described below:

[Measurement Method]

the hydrolysis degree after one week is a number average molecularweight reduction rate, compared to an initial number average molecularweight of the biodegradable polyester resin composition, of thebiodegradable polyester resin composition placed for one week underhigh-temperature and high-humidity conditions of 80° C. and a relativehumidity of 100%, and the hydrolysis degree after three weeks is anumber average molecular weight reduction rate, compared to an initialnumber average molecular weight of the biodegradable polyester resincomposition, of the biodegradable polyester resin composition placed forthree weeks under high-temperature and high-humidity conditions of 80°C. and a relative humidity of 100%.

In the biodegradable polyester resin composition according to anembodiment, a biodegradability after nine weeks may be 85% or more,wherein the biodegradability after nine weeks is a molecular weightreduction rate, compared to an initial molecular weight of thebiodegradable polyester resin composition, of the biodegradablepolyester resin composition placed at 60° C. and a relative humidity of90% for nine weeks under composting conditions.

In the biodegradable polyester resin composition according to anembodiment, a biodegradability after one week may be 45% to 75%, whereinthe biodegradability after one week is a molecular weight reductionrate, compared to an initial molecular weight of the biodegradablepolyester resin composition, of the biodegradable polyester resincomposition placed at 60° C. and a relative humidity of 90% for one weekunder composting conditions.

In the biodegradable polyester resin composition according to anembodiment, a hydrolysis degree after two weeks may be 80% to 95%,wherein the hydrolysis degree after two weeks is a number averagemolecular weight reduction rate, compared to an initial number averagemolecular weight of the biodegradable polyester resin composition, ofthe biodegradable polyester resin composition placed for two weeks underhigh-temperature and high-humidity conditions of 80° C. and a relativehumidity of 100%.

In the biodegradable polyester resin composition according to anembodiment, a hydrolysis degree after four weeks may be 85% or more,wherein the hydrolysis degree after four weeks is a number averagemolecular weight reduction rate, compared to an initial number averagemolecular weight of the biodegradable polyester resin composition, ofthe biodegradable polyester resin composition placed for four weeksunder high-temperature and high-humidity conditions of 80° C. and arelative humidity of 100%, and a hydrolysis degree increase rate fromone week to two weeks is 29%/week to 50%/week, and a hydrolysis degreeincrease rate from three weeks to four weeks is 0.01%/week to 3%/week.

In the biodegradable polyester resin composition according to anembodiment, a biodegradability after four weeks may be 73% to 85%,wherein the biodegradability after four weeks is a number averagemolecular weight reduction rate, compared to an initial number averagemolecular weight of the biodegradable polyester resin composition, ofthe biodegradable polyester resin composition placed for four weeksunder high-temperature and high-humidity conditions of 80° C. and arelative humidity of 100%, and a biodegradability increase rate from oneweek to four weeks is 3.5%/week to 8%/week.

In the biodegradable polyester resin composition according to anembodiment, an acid value of the biodegradable polyester resincomposition may be 2.0 mg KOH/g or less.

In the biodegradable polyester resin composition according to anembodiment, an oligomer having a molecular weight of 400 to 1300 may beincluded in an amount of 5000 ppm to 20000 ppm based on a total amountof the biodegradable polyester resin composition.

In the biodegradable polyester resin composition according to anembodiment, the oligomer may include the diol, the aromatic dicarboxylicacid and the aliphatic dicarboxylic acid.

In accordance with yet another aspect of the present disclosure, thereis provided a biodegradable molded article, including a biodegradableresin composition, wherein the biodegradable resin composition includesa polyester resin including a diol, an aromatic dicarboxylic acid and analiphatic dicarboxylic acid; and 5000 ppm to 20000 ppm of a hydrophilicregulator having a molecular weight of 400 to 1300.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of thepresent disclosure will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a diagram schematically illustrating an apparatus forproducing a polyester resin composition according to an embodiment; and

FIG. 2 illustrates an embodiment of a biodegradable molded articleformed of a polyester resin composition according to an embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the present disclosure will be described in more detailwith reference to the following embodiments. The scope of the presentdisclosure is not limited to the following embodiments and coversmodifications and equivalents of the technological aspects disclosedherein.

In the specification, when a certain part “includes” a certaincomponent, this indicates that the part may further include anothercomponent instead of excluding another component unless there is nodifferent disclosure.

In addition, it should be understood that all numerical rangesrepresenting physical property values, dimensions, etc. of componentsdescribed in this specification are modified by the term ‘about’ in allcases unless otherwise specified.

In this specification, terms such as first, second, primary, andsecondary are used to describe various components, and the componentsare not limited by the terms. The terms are only used for the purpose ofdistinguishing one component from another.

In this specification, ppm is a unit based on mass. The 1 ppm is 1 in 1million of the total mass. That is, the 1 ppm is 0.0001 wt % based onthe total mass.

The biodegradable polyester resin composition according to an embodimentincludes a biodegradable polyester resin. The biodegradable polyesterresin composition according to an embodiment may include thebiodegradable polyester resin alone or together with other resins oradditives.

The biodegradable polyester resin includes a diol, an aromaticdicarboxylic acid and an aliphatic dicarboxylic acid. The biodegradablepolyester resin includes a diol residue, an aromatic dicarboxylic acidresidue and an aliphatic dicarboxylic acid residue. The diol residue isderived from the diol, the aromatic dicarboxylic acid residue is derivedfrom the aromatic dicarboxylic acid, and the aliphatic dicarboxylic acidresidue is derived from the aliphatic dicarboxylic acid. Thebiodegradable polyester resin includes a diol component, an aromaticdicarboxylic acid component and an aliphatic dicarboxylic acidcomponent. Likewise, the diol component may be derived from the diol,the aromatic dicarboxylic acid component may be derived from thearomatic dicarboxylic acid, and the aliphatic dicarboxylic acidcomponent may be derived from the aliphatic dicarboxylic acid.

In a description of the biodegradable polyester resin compositionaccording to an embodiment, a diol residue may be expressed as a diol.In the biodegradable polyester resin, a dicarboxylic acid residue may beexpressed as dicarboxylic acid. In addition, the residue may beexpressed as a component.

The diol may be an aliphatic diol. The diol may be a bio-derived diol.The diol may be at least one selected from the group consisting ofethanediol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol,2,2-dimethyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol,2-ethyl-2-isobutyl-1,3-propanediol, 1,2-butanediol, 1,4-butanediol,1,5-pentanediol, 3-methyl-1,5-pentanediol,2,2,4-trimethyl-1,3-pentanediol, 1,6-hexanediol, 2-ethyl-1,3-hexanediol,2,4-dimethyl-2-ethyl-1,3-hexanediol, 2,2,4-trimethyl-1,6-hexanediol,2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol and1,12-octadecanediol or derivatives thereof.

The diol may be at least one selected from the group consisting of1,4-butanediol, 1,2-ethanediol, 1,3-propanediol, diethylene glycol andneopentyl glycol or derivatives thereof.

The diol may be at least one selected from the group consisting of1,4-butanediol, 1,2-ethanediol, 1,3-propanediol or derivatives thereof.

The diol may include 1,4-butanediol or a derivative thereof.

The aromatic dicarboxylic acid may be at least one selected from thegroup consisting of phthalic acid, terephthalic acid, isophthalic acid,1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid,2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid,4,4′-diphenyl dicarboxylic acid, 4,4′-diphenyl ether dicarboxylic acid,anthracen dicarboxylic acid, and phenanthren dicarboxylic acid orderivatives thereof.

The aromatic dicarboxylic acid may be at least one selected from thegroup consisting of terephthalic acid, dimethyl terephthalate,2,6-naphthalene dicarboxylic acid, isophthalic acid or derivativesthereof.

The aromatic dicarboxylic acid may include terephthalic acid, dimethylterephthalate or a derivative thereof.

The aliphatic dicarboxylic acid may be at least one selected from thegroup consisting of oxalic acid, malonic acid, succinic acid, maleicacid, fumaric acid, glutaric acid, adipic acid, pimelic acid, servericacid, azelaic acid, sebacic acid, dodecanedicarboxylic acid and1,4-cyclohexanedicarboxylic acid or derivatives thereof.

The aliphatic dicarboxylic acid may be at least one selected from thegroup consisting of adipic acid, succinic acid and sebacic acid orderivatives thereof.

The aliphatic dicarboxylic acid may include an adipic acid or aderivative thereof.

In the biodegradable polyester resin, a molar ratio of all diol residuesincluding the diol to all dicarboxylic acid residues including thearomatic dicarboxylic acid and the aliphatic dicarboxylic acid may rangefrom about 1:0.9 to about 1:1.1. A molar ratio of all diol residues toall dicarboxylic acid residues may range from about 1:0.95 to about1:1.05.

In the biodegradable polyester resin, a molar ratio of the aromaticdicarboxylic acid residue to the aliphatic dicarboxylic acid residue mayrange from about 3:7 to about 7:3. In the biodegradable polyester resin,a molar ratio of the aromatic dicarboxylic acid residue to the aliphaticdicarboxylic acid residue may range from about 3.3:6.7 to about 6.7:3.3.In the biodegradable polyester resin, a molar ratio of the aromaticdicarboxylic acid residue to the aliphatic dicarboxylic acid residue mayrange from about 4:6 to about 6:4. In the biodegradable polyester resin,a molar ratio of the aromatic dicarboxylic acid residue to the aliphaticdicarboxylic acid residue may range from about 4.2:5.8 to about 5:5.

The biodegradable polyester resin may include a diol residue derivedfrom 1,4-butanediol in a content ranging from about 90 mol % or morebased on the total diol. The biodegradable polyester resin may include adiol residue derived from 1,4-butanediol in a content ranging from about95 mol % or more based on the total diol. The biodegradable polyesterresin may include a diol residue derived from 1,4-butanediol in acontent ranging from about 98 mol % or more based on the total diol.

The biodegradable polyester resin may include an aromatic dicarboxylicacid residue derived from terephthalic acid or dimethyl terephthalate ina content ranging from about mol % to about 70 mol % based on the totaldicarboxylic acid. The biodegradable polyester resin may include anaromatic dicarboxylic acid residue derived from terephthalic acid ordimethyl terephthalate in a content ranging from about 35 mol % to about65 mol % based on the total dicarboxylic acid. The biodegradablepolyester resin may include a dicarboxylic acid residue derived fromterephthalic acid or dimethyl terephthalate in a content ranging fromabout 40 mol % to about 59 mol % based on the total dicarboxylic acid.The biodegradable polyester resin may include an aromatic dicarboxylicacid residue derived from terephthalic acid or dimethyl terephthalate ina content ranging from about 43 mol % to about 53 mol % based on thetotal dicarboxylic acid.

The biodegradable polyester resin may include an aliphatic dicarboxylicacid residue derived from adipic acid in a content ranging from about 30mol % to about 70 mol % based on the total dicarboxylic acid. Thebiodegradable polyester resin may include an aliphatic dicarboxylic acidresidue derived from adipic acid in a content ranging from about 35 mol% to about 65 mol % based on the total dicarboxylic acid. Thebiodegradable polyester resin may include an aliphatic dicarboxylic acidresidue derived from adipic acid in a content ranging from about 41 mol% to about 60 mol % based on the total dicarboxylic acid. Thebiodegradable polyester resin may include an aliphatic dicarboxylic acidresidue derived from adipic acid in a content ranging from about 47 mol% to about 57 mol % based on the total dicarboxylic acid.

In addition, the biodegradable polyester resin may include at least onefirst block and at least one second block. The biodegradable polyesterresin may have a molecular structure in which the first block and thesecond block are alternately bonded.

The first block may include the diol residue and the aromaticdicarboxylic acid residue. The first block may be formed byesterification of the diol and the aromatic dicarboxylic acid. The firstblock may include only the diol residue and the aromatic dicarboxylicacid residue. The first block may include only repeating units formed bythe esterification of the diol and the aromatic dicarboxylic acid. Thatis, the first block may mean the sum of repeating units of the diol andthe aromatic dicarboxylic acid before being combined with the aliphaticdicarboxylic acid.

The second block may include the diol residue and the aliphaticdicarboxylic acid residue. The second block may be formed byesterification of the diol and the aliphatic dicarboxylic acid. Thesecond block may include only the diol residue and the aliphaticdicarboxylic acid residue. The second block may include only repeatingunits formed by the esterification of the diol and the aliphaticdicarboxylic acid. That is, the second block may mean the sum ofrepeating units of the diol and the aliphatic dicarboxylic acid beforebeing combined with the aromatic dicarboxylic acid.

In the biodegradable polyester resin, a ratio (X/Y) of the number (X) ofthe first blocks to the number (Y) of the second blocks may range fromabout 0.5 to about 1.5. In the biodegradable polyester resin, the ratio(X/Y) of the number (X) of the first blocks to the number (Y) of thesecond blocks may range from about 0.6 to about 1.4. In thebiodegradable polyester resin, the ratio (X/Y) of the number (X) of thefirst blocks to the number (Y) of the second blocks may range from about0.7 to about 1.3. In the biodegradable polyester resin, the ratio (X/Y)of the number (X) of the first blocks to the number (Y) of the secondblocks may range from about 0.75 to about 1.2. In addition, in thebiodegradable polyester resin, the ratio (X/Y) of the number (X) of thefirst blocks to the number (Y) of the second blocks may be 0.8 to 1. Thenumber of the first blocks may be smaller than the number of the secondblocks.

The number of the first blocks may range from about 30 to about 300. Thenumber of the first blocks may range from about 40 to about 250. Thenumber of the first blocks may range from about 50 to about 220. Thenumber of the first blocks may range from about 60 to about 200. Thenumber of the first blocks may range from about 70 to about 200. Thenumber of the first blocks may range from about 75 to about 200.

The number of the first blocks may vary depending upon the content ofthe aromatic dicarboxylic acid, the molecular weight of thebiodegradable polyester resin and an alternation ratio to be describedbelow. That is, the number of the first blocks may increase as a molarratio of the aromatic dicarboxylic acid increases, as the molecularweight of the biodegradable polyester resin increases, and as analternation ratio to be described below increases.

The number of the second blocks may range from about 30 to about 300.The number of the second blocks may range from about 40 to about 250.The number of the second blocks may range from about 50 to about 220.The number of the second blocks may range from about 60 to about 200.The number of the second blocks may range from about 70 to about 200.The number of the second blocks may range from about 75 to about 200.

The number of the second blocks may vary depending upon the content ofthe aliphatic dicarboxylic acid, the molecular weight of thebiodegradable polyester resin and a polymerization process describedbelow. That is, the molecular weight of the biodegradable polyesterresin may increase as the molar ratio of the aliphatic dicarboxylic acidincreases, so that the number of the first blocks may increase.

When the biodegradable polyester resin includes the first block and thesecond block within the specified range above, the biodegradablepolyester resin composition according to an embodiment may haveappropriate biodegradability while having appropriate mechanicalstrength. In addition, when the biodegradable polyester resin includesthe first block and the second block within the specified range above,the biodegradable polyester resin composition according to an embodimentmay have improved stiffness while having improved flexibility.Accordingly, the biodegradable polyester resin composition according toan embodiment may be used for an injection-molded article, etc. Inaddition, when the biodegradable polyester resin includes the firstblock and the second block within the specified range above, thebiodegradable polyester resin composition according to an embodiment mayhave appropriate biodegradability while having appropriate durability toultraviolet light, and the like.

The first block may be represented by Formula 1 below:

-   -   where R1 is a substituted or unsubstituted arylene group having        6 to 20 carbon atoms, R2 is a substituted or unsubstituted        alkylene group having 1 to 20 carbon atoms, and m is 1 to 20.

R1 may be a substituted or unsubstituted phenylene group, and R2 may bea butylene group.

The second block may be represented by Formula 2 below:

-   -   where R3 and R4 are each independently a substituted or        unsubstituted alkylene group having 1 to 20 carbon atoms, and n        is 1 to 20.

R3 and R4 may be a butylene group.

The biodegradable polyester resin may have a structure in which thefirst block and the second block are alternately bonded to each other.The biodegradable polyester resin may be represented by Formula 3 below.

-   -   where R1 is a substituted or unsubstituted arylene group having        6 to 20 carbon atoms, R2 is a substituted or unsubstituted        alkylene group having 1 to 20 carbon atoms, and m is 1 to 20. In        addition, R3 and R4 are each independently a substituted or        unsubstituted alkylene group having 1 to 20 carbon atoms, and n        is 1 to 20.

The diol residue may include a residue of 1,4-butanediol or derivativethereof, the aromatic dicarboxylic acid residue may include a residue ofterephthalic acid or derivative thereof, and the aliphatic dicarboxylicacid residue may include a residue of adipic acid or derivative thereof.

For example, the biodegradable polyester resin may include a first blockincluding a residue of 1,4-butanediol or derivative thereof and aresidue of terephthalic acid or derivative thereof.

Alternatively, the biodegradable polyester resin may include a firstblock including a residue of 1,4-butanediol or derivative thereof and aresidue of dimethyl terephthalate or derivative thereof.

The biodegradable polyester resin may include a second block including aresidue of 1,4-butanediol or derivative thereof and a residue of adipicacid or derivative thereof.

Alternatively, the biodegradable polyester resin may include a secondblock including a residue of 1,4-butanediol or derivative thereof and aresidue of succinic acid or derivative thereof.

A biodegradable polyester resin according to an embodiment of thepresent disclosure may include a first block including a residue of1,4-butanediol or derivative thereof and a residue of terephthalic acidor derivative thereof; and a second block including a residue of1,4-butanediol or derivative thereof and a residue of adipic acid orderivative thereof.

The first block may be represented by Formula 4 below, and the secondblock may be represented by Formula 5 below:

-   -   where m is 1 to 20.

-   -   where n is 1 to 20.

The biodegradable polyester resin may be represented by Formula 6 below:

-   -   where m is 1 to 20, and n is 1 to 20.

When m of the first block and n of the second block falls within thespecified range, it may be more advantageous to provide a biodegradablepolyester sheet, film or molded article having excellentbiodegradability and water degradability and improved properties.

In addition, when the biodegradable polyester resin includes the firstblock and the second block within the specified range above, thebiodegradable polyester resin composition according to an embodiment mayhave appropriate mechanical properties and appropriate UV resistance.

Since the first and second blocks have the characteristics, themechanical properties of the biodegradable polyester resin compositionaccording to an embodiment may be improved.

Since the first and second blocks have the characteristics, thebiodegradable polyester resin composition according to an embodiment mayhave appropriate UV resistance, biodegradation rate, and hydrolysisrate.

The biodegradable polyester resin may further include a branching agent.The branching agent may include at least one selected from the groupconsisting of a trihydric or higher alcohol, an anhydride and atrihydric or higher carboxylic acid. The branching agent may react withthe diol, the aromatic dicarboxylic acid and the aliphatic dicarboxylicacid. Accordingly, the branching agent may be included as a part of themolecular structure of the biodegradable polyester resin.

The trihydric or higher alcohol may be at least one selected from thegroup consisting of glycerol, pentaerythritol or trimethylolpropane.

The trihydric or higher carboxylic acid may be at least one selectedfrom the group consisting of methane tricarboxylic acid,ethanetricarboxylic acid, citric acid, benzene-1,3,5-tricarboxylic acid,5-sulfo-1,2,4-benzenetricarboxylic acid, ethane-1,1,2,2-tetracarboxylicacid, propane-1,1,2,3-tetracarboxylic acid,butane-1,2,3,4-tetracarboxylic acid,cyclopentane-1,2,3,4-tetracarboxylic acid andbenzene-1,2,4,5-tetracarboxylic acid.

The anhydride may include at least one selected from the groupconsisting of trimellitic anhydride, succinic anhydride, methyl succinicanhydride, ethylsuccinic anhydride, 2,3-butanedicarboxylic anhydride,2,4-pentanedicarboxylic anhydride, 3,5-heptanedicarboxylic anhydride,1,2,3,4-butanetetracarboxylic dianhydride, maleic anhydride, dodecylsuccinic anhydride and pyromellitic anhydride.

The branching agent may be included in a content ranging from about 0.1wt % to about 5 wt % in the biodegradable polyester resin based on thetotal amount of the biodegradable polyester resin. The branching agentmay be included in a content ranging from about 0.1 wt % to about 3 wt %in the biodegradable polyester resin based on the total amount of thebiodegradable polyester resin. The branching agent may be included in acontent ranging from about 0.1 wt % to about 1 wt % in the biodegradablepolyester resin based on the total amount of the biodegradable polyesterresin.

Since the biodegradable polyester resin includes the branching agentwithin the specified range above, the biodegradable polyester resincomposition according to an embodiment may have appropriate mechanicalcharacteristics and appropriate biodegradability.

The biodegradable polyester resin composition according to an embodimentmay include the biodegradable resin in a content ranging from about 30wt % or more based on the total weight of the composition. Thebiodegradable polyester resin composition according to an embodiment mayinclude the biodegradable resin in a content ranging from about 50 wt %or more based on the total weight of the composition. The biodegradablepolyester resin composition according to an embodiment may include thebiodegradable resin in a content ranging from about 70 wt % or morebased on the total weight of the composition. The biodegradablepolyester resin composition according to an embodiment may include thebiodegradable resin in a content ranging from about 80 wt % or morebased on the total weight of the composition. The biodegradablepolyester resin composition according to an embodiment may include thebiodegradable resin in a content ranging from about 90 wt % or morebased on the total weight of the composition. The biodegradablepolyester resin composition according to an embodiment may include thebiodegradable resin in a content ranging from about 95 wt % or morebased on the total weight of the composition. The biodegradablepolyester resin composition according to an embodiment may include thebiodegradable resin in a content ranging from about 99 wt % or morebased on the total weight of the composition. A maximum content of thebiodegradable resin in the biodegradable polyester resin compositionaccording to an embodiment may range from about 100 wt % based on thetotal weight of the composition.

The biodegradable polyester resin composition according to an embodimentmay further include a reinforcing material. The reinforcing material mayimprove the mechanical properties of the biodegradable polyester resincomposition according to an embodiment and the mechanical properties ofa film or molded article made of the composition. In addition, thereinforcing material may control the deformation characteristics of thebiodegradable polyester resin composition according to an embodiment dueto ultraviolet rays. In addition, the reinforcing material may controlthe hydrolysis characteristics of the biodegradable polyester resincomposition according to an embodiment. In addition, the reinforcingmaterial may control the biodegradability of the biodegradable polyesterresin according to an embodiment.

The reinforcing material may be a fiber derived from biomass. Thereinforcing material may be a fiber made of an organic material. Thereinforcing material may be nanocellulose.

The nanocellulose may be one or more selected from the group consistingof nanocrystalline cellulose, cellulose nanofiber, microfibrillatedcellulose, hydroxymethyl cellulose, hydroxyethyl cellulose,hydroxypropyl cellulose, hydroxypropylmethyl cellulose, celluloseacetate, methyl cellulose, ethyl cellulose, propyl cellulose, butylcellulose, pentyl cellulose, hexyl cellulose and cyclohexyl cellulose.

The nanocellulose may include an ion-bonded metal. The nanocrystallinecellulose may include elemental sodium. In addition, the nanocrystallinecellulose may include sulphate.

The nanocrystalline cellulose may include a carboxylate. Thenanocrystalline cellulose may include a cellulose hydrogen sulphatesodium salt (Cellulose hydrogen sulphate sodium salt.

The nanocellulose may be represented by Formula 7 below:

[(C₆H₁₀O₅)_(x)SO₃Na],  [Formula 7]

-   -   where x is 1 to 35, and y is 1 to 10.

The specific surface area of the nanocellulose may range from about 200m²/g to about 600 m²/g. The specific surface area of the nanocellulosemay range from about 250 m²/g to about 500 m²/g.

The weight average molecular weight of the nanocellulose may range fromabout 10000 g/mol to about 40000 g/mol. The weight average molecularweight of the nanocrystalline cellulose may range from about 11000 g/molto about 35000 g/mol.

The moisture content of the nanocrystalline cellulose may range fromabout 2 wt % to about 8 wt %. The moisture content of thenanocrystalline cellulose may range from about 4 wt % to about 6 wt %.

The average diameter of the nanocellulose may range from about 0.5 nm toabout nm. The average diameter of the nanocellulose may range from about1 nm to about 8 nm. The average diameter of the nanocellulose may rangefrom about 1.5 nm to about 7 nm.

The average length of the nanocellulose may range from about 20 nm toabout 300 nm. The average length of the nanocellulose may range fromabout 30 nm to about 180 nm. The average length of the nanocellulose mayrange from about 35 nm to about 150 nm.

When the diameter and length of the nanocellulose satisfy the ranges,the biodegradability and properties of the biodegradable polyester resinor the biodegradability and properties of a biodegradable polyestersheet, film and molded article made using the biodegradable polyesterresin may be further improved.

The diameter and length of the nanocellulose may be measured by atomicforce microscopy in a water-dispersed state.

The sulfur content of the nanocellulose may range from about 0.1 wt % toabout 1.2 wt % based on the total amount of the nanocrystallinecellulose. The sulfur content of the nanocellulose may range from about0.2 wt % to about 1.1 wt % based on the total amount of thenanocellulose.

The pH of the nanocellulose may be 5 to 8. The pH of the nanocellulosemay be 6 to 8.

The zeta potential of the nanocellulose may range from about −25 mV toabout −50 mV. The zeta potential of the nanocellulose may range fromabout −30 mV to about −45 mV.

The nanocellulose may be included in a content ranging from about 0.01parts by weight to about 2 parts by weight in the biodegradablepolyester resin composition according to an embodiment based on 100parts by weight of the biodegradable polyester resin. The nanocellulosemay be included in a content ranging from about 0.03 parts by weight toabout 1.5 parts by weight in the biodegradable polyester resincomposition according to an embodiment based on 100 parts by weight ofthe biodegradable polyester resin. The nanocellulose may be included ina content ranging from about 0.04 parts by weight to about 1.2 parts byweight in the biodegradable polyester resin composition according to anembodiment based on 100 parts by weight of the biodegradable polyesterresin. The nanocellulose may be included in a content ranging from about0.05 parts by weight to about 1 part by weight in the biodegradablepolyester resin composition according to an embodiment based on 100parts by weight of the biodegradable polyester resin.

Since the nanocellulose has the aforementioned characteristics, it maybe uniformly dispersed in the biodegradable polyester resin compositionaccording to an embodiment.

Since the nanocellulose has the aforementioned characteristics, it mayimprove the mechanical properties of the biodegradable polyester resincomposition according to an embodiment.

In addition, the nanocellulose severs as a nucleating agent, therebybeing capable of improving the crystallization rate of the biodegradablepolyester resin composition according to an embodiment. Accordingly, thenanocellulose may increase the crystallization temperature of thebiodegradable polyester resin composition according to an embodiment.

Since the nanocellulose has the characteristics, the biodegradablepolyester resin composition according to an embodiment may haveappropriate UV resistance.

Since the nanocellulose has the characteristics, the biodegradablepolyester resin composition according to an embodiment may have anappropriate biodegradation rate.

Since the nanocellulose has the characteristics, the biodegradablepolyester resin composition according to an embodiment may have anappropriate hydrolysis rate.

The biodegradable polyester resin composition according to an embodimentmay include a metal salt.

The metal salt may be included in a content ranging from about 0.1 ppmto about 1000 ppm based on the total weight of the biodegradablepolyester resin composition according to an embodiment. The metal saltmay be included in a content ranging from about 1 ppm to about 500 ppmbased on the total weight of the biodegradable polyester resincomposition according to an embodiment. The metal salt may be includedin a content ranging from about 1 ppm to about 100 ppm based on thetotal weight of the biodegradable polyester resin composition accordingto an embodiment. The metal salt may be included in a content rangingfrom about 1 ppm to about 50 ppm based on the total weight of thebiodegradable polyester resin composition according to an embodiment.

The metal salt may be at least one selected from the group consisting ofa nitrate, a sulfate, hydrochloride, a carboxylate and the like. Themetal salt may be at least one selected from the group consisting oftitanium salt, silicon salt, sodium salt, calcium salt, potassium salt,magnesium salt, copper salt, iron salt, aluminum salt, silver salt andthe like. The metal salt may be at least one selected from the groupconsisting of magnesium acetate, calcium acetate, potassium acetate,copper nitrate, silver nitrate, sodium nitrate, and the like.

The metal salt may include one or more selected from the groupconsisting of iron (Fe), magnesium (Mg), nickel (Ni), cobalt (Co),copper (Cu), palladium (Pd), zinc (Zn), vanadium (V), titanium, (Ti),indium (In), manganese (Mn), silicon (Si) and tin (Sn).

In addition, the metal salt may be selected from the group consisting ofacetate, nitrate, nitride, sulfide, sulfate, sulfoxide, hydroxide,hydrate, chloride, chlorinate and bromide.

Since the biodegradable polyester resin composition according to anembodiment includes the metal salt within the specified content above, ahydrolysis rate and a biodegradation rate may be appropriatelycontrolled.

Since the biodegradable polyester resin composition according to anembodiment includes the metal salt within the specified content above, ahydrolysis rate and a biodegradation rate may be appropriatelycontrolled.

The biodegradable polyester resin composition according to an embodimentmay further include an anti-hydrolysis agent.

The anti-hydrolysis agent may be at least one selected from amongsilicone-based compounds such as silane, silazane and siloxane.

The anti-hydrolysis agent may include alkoxy silane. The anti-hydrolysisagent may include trimethoxy silane and/or triethoxy silane. Theanti-hydrolysis agent may include alkoxy silane including an epoxygroup. The anti-hydrolysis agent may include at least one selected fromthe group consisting of 2-(3,4-epoxycyclohexyl) ethyltrimethoxysilane,3-glycidoxypropyl methyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyl methyldiethoxysilane and3-glycidoxypropyl triethoxysilane.

The anti-hydrolysis agent may be included in a content ranging fromabout 1 ppm to about 10000 ppm in the biodegradable polyester resincomposition according to an embodiment. The anti-hydrolysis agent may beincluded in a content ranging from about 1 ppm to about 1000 ppm in thebiodegradable polyester resin composition according to an embodiment.The anti-hydrolysis agent may be included in a content ranging fromabout 5 ppm to 500 ppm in the biodegradable polyester resin compositionaccording to an embodiment. The anti-hydrolysis agent may be included ina content ranging from about 10 ppm to 300 ppm in the biodegradablepolyester resin composition according to an embodiment.

The anti-hydrolysis agent may be bonded to the biodegradable polyesterresin. The anti-hydrolysis agent may be chemically bonded to thebiodegradable polyester resin. The anti-hydrolysis agent may bechemically bonded to a polymer included in the biodegradable polyesterresin. The anti-hydrolysis agent may couple polymers included in thebiodegradable polyester resin.

Since the biodegradable polyester resin composition according to anembodiment includes the anti-hydrolysis agent within the specified rangeabove, it may have appropriate hydrolysis resistance. In particular,since the biodegradable polyester resin according to an embodimentincludes the anti-hydrolysis agent within the specified range above, itmay have appropriate initial hydrolysis characteristics and improvedbiodegradability.

Accordingly, the biodegradable polyester resin composition according toan embodiment may include a silicon element. The biodegradable polyesterresin composition according to an embodiment may include the siliconelement in a content ranging from about 1 ppm to about 150 ppm. Thebiodegradable polyester resin composition according to an embodiment mayinclude the silicon element in a content ranging from about 0.1 ppm toabout 100 ppm. The biodegradable polyester resin composition accordingto an embodiment may include the silicon element in a content rangingfrom about 0.1 ppm to about 50 ppm. The biodegradable polyester resincomposition according to an embodiment may include the silicon elementin a content ranging from about 0.1 ppm to about 20 ppm.

In addition, the anti-hydrolysis agent may also react with a terminalcarboxyl group or an unreacted carboxyl group. Accordingly, thebiodegradable polyester resin composition according to an embodiment mayhave a low acid value.

In addition, the anti-hydrolysis agent may couple polymers included inthe biodegradable polyester resin, so that the biodegradable polyesterresin composition according to an embodiment may increase the ratio ofhigh-molecular-weight polymers. Accordingly, the mechanical propertiesof the biodegradable polyester resin composition according to anembodiment may be improved.

The biodegradable polyester resin composition according to an embodimentmay further include a chain extender.

The chain extender may include isocyanate.

The chain extender may be at least one selected from the groupconsisting of monofunctional isocyanate or polyfunctional isocyanate.

The chain extender may be at least one selected from the groupconsisting of tolylene 2,4-diisocyanate, tolylene 2,6-diisocyanate,diphenylmethane 4,4′-diisocyanate and 2,4′-diisocyanate, naphthalene1,5-diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate,pentamethylene diisocyanate, isophorone diisocyanate andmethylenebis(4-isocyanatocyclohexane).

The chain extender may include triisocyanate. The chain extender mayinclude tri(4-isocyanatophenyl)methane.

The chain extender may include an acrylic polymer. The acrylic polymermay include an acryl group. The acryl group may be bonded to a mainchain as a side chain. The acrylic polymer may include an epoxy group.The epoxy group may be bonded to the main chain as a side chain.

The chain extender may include a styrene-based polymer. The chainextender may include a styrene-based glycidyl acrylate.

The chain extender may be chemically bonded to the biodegradablepolyester resin. The chain extender may be chemically bonded to apolymer included in the biodegradable polyester resin. The chainextender may be bonded to a terminal of the polymer included in thebiodegradable polyester resin. In addition, the chain extender may bebonded to terminals of three polymers included in the biodegradablepolyester resin.

The chain extender may be a terminal capping agent for capping aterminal of the polymer.

The chain extender may be included in the biodegradable polyester resincomposition according to an embodiment in a content ranging from about0.1 wt % to about 10 wt % based on the total amount of the composition.The chain extender may be included in the biodegradable polyester resincomposition according to an embodiment in a content ranging from about0.2 wt % to about 8 wt % based on the total amount of the composition.The chain extender may be included in the biodegradable polyester resincomposition according to an embodiment in a content ranging from about0.3 wt % to about 7 wt % based on the total amount of the composition.

When the biodegradable polyester resin composition according to anembodiment includes the chain extender within the specified range above,it may have appropriate hydrolysis resistance and appropriatebiodegradability.

In addition, the chain extender may react with a terminal carboxyl groupor an unreacted carboxyl group. Accordingly, the biodegradable polyesterresin composition according to an embodiment may have a low acid value.

In addition, the chain extender couples polymers included in thebiodegradable polyester resin, so that the biodegradable polyester resincomposition according to an embodiment may increase the ratio ofhigh-molecular-weight polymers. Accordingly, the mechanical propertiesof the biodegradable polyester resin composition according to anembodiment may be improved.

The biodegradable polyester resin composition according to an embodimentmay include an oligomer. The molecular weight of the oligomer may rangefrom about 400 to about 1300.

The oligomer may be included in the biodegradable polyester resincomposition according to an embodiment in a content ranging from about3000 ppm to about 30000 ppm based on the total amount of the resincomposition. The oligomer may be included in the biodegradable polyesterresin composition according to an embodiment in a content ranging fromabout 5000 ppm to about 20000 ppm based on the total amount of the resincomposition. The oligomer may be included in the biodegradable polyesterresin composition according to an embodiment in a content ranging fromabout 5000 ppm to about 15000 ppm based on the total amount of the resincomposition. The oligomer may be included in the biodegradable polyesterresin composition according to an embodiment in a content ranging fromabout 7000 ppm to about 15000 ppm based on the total amount of the resincomposition.

The oligomer may be a reaction product of at least two or more of thediol, the aromatic dicarboxylic acid and the aliphatic dicarboxylicacid. The oligomer may be a reaction product of 1,4-butanediol,terephthalic acid and adipic acid.

The oligomer may include an oligomer in which a molar ratio of thealiphatic dicarboxylic acid is higher than that of the aromaticdicarboxylic acid. In the oligomer, a ratio of an oligomer containing arelatively large amount of the aliphatic dicarboxylic acid may be higherthan a ratio of an oligomer containing a relatively large amount of thearomatic dicarboxylic acid.

The oligomer may include a first oligomer, a second oligomer, a thirdoligomer and a fourth oligomer.

The first oligomer may have a molecular weight of 415 to 425. The firstoligomer may have a molecular weight of 419 to 424.

The first oligomer may be a reaction product formed by reacting two1,4-butanediol molecules, one terephthalic acid molecule and one adipicacid molecule. That is, the first oligomer may include the1,4-butanediol, the terephthalic acid and the adipic acid in a molarratio of 2:1:1. In addition, the first oligomer may have four esterbonds. The first oligomer may have a ring structure.

In addition, the first oligomer may include one first unit representedby Formula 6 below and one second unit represented by Formula 7 below:

The first oligomer may have a ring structure. The first oligomer mayinclude the first and second units and may have a ring structure.

The first oligomer may be represented by Formula 8 below:

The content of the first oligomer may range from about 1000 ppm to about6000 ppm based on the total amount of the biodegradable polyester resincomposition according to an embodiment. The content of the firstoligomer may range from about 1500 ppm to about 5000 ppm based on thetotal amount of the biodegradable polyester resin composition accordingto an embodiment. The content of the first oligomer may range from about2000 ppm to about 4500 ppm based on the total amount of thebiodegradable polyester resin composition according to an embodiment.The content of the first oligomer may range from about 2500 ppm to about5000 ppm based on the total amount of the biodegradable polyester resincomposition according to an embodiment.

The second oligomer may have a molecular weight of 620 to 630. Thesecond oligomer may have a molecular weight of 621 to 626.

The second oligomer may be a reaction product formed by reacting three1,4-butanediol molecules, one terephthalic acid molecule and two adipicacid molecules. That is, the second oligomer may include the1,4-butanediol, the terephthalic acid and the adipic acid in a molarratio of 3:1:2. In addition, the second oligomer may have six esterbonds.

The second oligomer may include one first unit represented by the aboveFormula 6 and two second units represented by the above Formula 7.

The second oligomer may be at least one selected from the groupconsisting of Formulas 9, 10 and 11 below:

The content of the second oligomer may range from about 1000 ppm toabout 5000 ppm based on the total amount of the biodegradable polyesterresin composition according to an embodiment. The content of the secondoligomer may range from about 1200 ppm to about 4500 ppm based on thetotal amount of the biodegradable polyester resin composition accordingto an embodiment. The content of the second oligomer may range fromabout 1500 ppm to about 4000 ppm based on the total amount of thebiodegradable polyester resin composition according to an embodiment.The content of the second oligomer may range from about 2000 ppm toabout 3800 ppm based on the total amount of the biodegradable polyesterresin composition according to an embodiment.

The third oligomer may have a molecular weight of 640 to 650. The thirdoligomer may have a molecular weight of 641 to 645.

The third oligomer may be a reaction product formed by reacting three1,4-butanediol molecules, two terephthalic acid molecules and one adipicacid molecule. That is, the third oligomer may include the1,4-butanediol, the terephthalic acid and the adipic acid in a molarratio of 3:2:1. In addition, the third oligomer may have six esterbonds.

The third oligomer may include two first units represented by the aboveFormula 6 and one second unit represented by the above Formula 7.

The third oligomer may be at least one selected from the groupconsisting of Formulas 12, 13 and 14 below:

The content of the third oligomer may range from about 300 ppm to about3000 ppm based on the total amount of the biodegradable polyester resincomposition according to an embodiment. The content of the thirdoligomer may range from about 500 ppm to about 2500 ppm based on thetotal amount of the biodegradable polyester resin composition accordingto an embodiment. The content of the third oligomer may range from about700 ppm to about 2000 ppm based on the total amount of the biodegradablepolyester resin composition according to an embodiment. The content ofthe third oligomer may range from about 800 ppm to about 1800 ppm basedon the total amount of the biodegradable polyester resin compositionaccording to an embodiment.

The fourth oligomer may have a molecular weight of 840 to 850. Thefourth oligomer may have a molecular weight of 841 to 845.

The fourth oligomer may include a reaction product formed by reactingfour 1,4-butanediol molecules, two terephthalic acid molecules and twoadipic acid molecules. That is, the fourth oligomer may include the1,4-butanediol, the terephthalic acid and the adipic acid in a molarratio of 4:2:2. In addition, the fourth oligomer may have eight esterbonds.

The fourth oligomer may include two first units represented by the aboveFormula 6 and two second units represented by the above Formula 7.

In addition, the fourth oligomer may include at least one of thefollowing bonded structures:

-   -   First unit-first unit-second unit-second unit,    -   First unit-second unit-first unit-second unit,    -   First unit-second unit-second unit-first unit, or    -   Second unit-first unit-first unit-second unit.

The content of the fourth oligomer may range from about 300 ppm to about3500 ppm based on the total amount of the biodegradable polyester resincomposition according to an embodiment. The content of the fourtholigomer may range from about 500 ppm to about 3000 ppm based on thetotal amount of the biodegradable polyester resin composition accordingto an embodiment. The content of the fourth oligomer may range fromabout 700 ppm to about 2500 ppm based on the total amount of thebiodegradable polyester resin composition according to an embodiment.The content of the fourth oligomer may range from about 800 ppm to about2000 ppm based on the total amount of the biodegradable polyester resincomposition according to an embodiment.

A ratio (the content of the first oligomer/the content of the totaloligomers) of the first oligomer based on the total oligomers may rangefrom about 0.20 to about 0.5. The ratio of the first oligomer based onthe total oligomers may range from about 0.25 to about 0.45. The ratioof the first oligomer based on the total oligomers may range from about0.30 to about 0.45. The ratio of the first oligomer based on the totaloligomers may range from about 0.32 to about 0.43.

A ratio (the content of the second oligomer/the content of the totaloligomers) of the second oligomer based on the total oligomers may rangefrom about 0.15 to about 0.45. The ratio of the second oligomer based onthe total oligomers may range from about 0.20 to 0.40. The ratio of thesecond oligomer based on the total oligomers may range from about 0.23to 0.37. The ratio of the second oligomer based on the total oligomersmay range from about 0.25 to 0.36.

A ratio (the content of the third oligomer/the content of the totaloligomers) of the third oligomer based on the total oligomers may rangefrom about 0.05 to about 0.25. The ratio of the third oligomer based onthe total oligomers may range from about 0.07 to 0.20. The ratio of thethird oligomer based on the total oligomers may range from about 0.08 to0.17. The ratio of the third oligomer based on the total oligomers mayrange from about 0.09 to 0.16.

A ratio (the content of the fourth oligomer/the content of the totaloligomers) of the fourth oligomer based on the total oligomers may rangefrom about 0.05 to about 0.30. The ratio of the fourth oligomer based onthe total oligomers may range from about 0.07 to 0.25. The ratio of thefourth oligomer based on the total oligomers may range from about 0.08to 0.22. The ratio of the fourth oligomer based on the total oligomersmay range from about 0.09 to 0.19.

A ratio (the content of the second oligomer/the content of the firstoligomer) of the second oligomer based on the first oligomer may rangefrom about 0.5 to about 1.2. The ratio of the second oligomer based onthe first oligomer may range from about 0.55 to about 1.0. The ratio ofthe second oligomer based on the first oligomer may range from about 0.6to about 0.95. The ratio of the second oligomer based on the firstoligomer may range from about 0.7 to about 0.9.

A ratio (the content of the third oligomer/the content of the firstoligomer) of the third oligomer based on the first oligomer may rangefrom about 0.2 to about 0.6. The ratio of the third oligomer based onthe first oligomer may range from about 0.22 to about 0.50. The ratio ofthe third oligomer based on the first oligomer may range from about 0.23to about 0.45. The ratio of the third oligomer based on the firstoligomer may range from about 0.25 to about 0.42.

A ratio (the content of the fourth oligomer/the content of the firstoligomer) of the fourth oligomer based on the first oligomer may rangefrom about 0.25 to about 0.65. The ratio of the fourth oligomer based onthe first oligomer may range from about 0.27 to about 0.55. The ratio ofthe fourth oligomer based on the first oligomer may range from about0.30 to about 0.50. The ratio of the fourth oligomer based on the firstoligomer may range from about 0.30 to about 0.48.

The second oligomer may be included in the total oligomers in a highercontent than the third oligomer.

A ratio (the content of the third oligomer/the content of the secondoligomer) of the third oligomer based on the second oligomer may rangefrom about 0.2 to about 0.6. A ratio (the content of the thirdoligomer/the content of the second oligomer) of the third oligomer basedon the second oligomer may range from about 0.24 to about 0.5. A ratio(the content of the third oligomer/the content of the second oligomer)of the third oligomer based on the second oligomer may range from about0.27 to about 0.45.

The molecular weights and contents of the oligomers may be measured byliquid chromatography mass spectrometry.

First, the biodegradable polyester resin composition according to anembodiment or the biodegradable polyester film according to anembodiment is pulverized and classified to produce a powder having anaverage particle diameter (D50) of about 50 μm. Next, the powder isimmersed in an organic solvent such as acetonitrile at room temperaturefor about 24 hours. Next, after a supernatant of the organic solvent issampled, the molecular weight and content of the oligomer may bemeasured by the liquid chromatography mass spectrometry. In addition, tomeasure the content of the oligomer, dibutyl phthalate may be used as astandard material and a calibration curve may be obtained.

The oligomer may be a hydrophilic regulator capable of adjusting thehydrophilicity and/or hydrophobicity of the biodegradable polyesterresin composition according to an embodiment. Accordingly, the oligomermay appropriately control the hydrolysis degree of the biodegradableresin composition according to an embodiment. The oligomer may be ahydrolysis regulator that appropriately controls the hydrolysis degreeof the biodegradable resin composition according to an embodiment.

In addition, the oligomer may appropriately control the biodegradabilityof the biodegradable resin composition according to an embodiment. Theoligomer may be a biodegradation regulator that appropriately controlsthe biodegradability of the biodegradable resin composition according toan embodiment.

Since the biodegradable resin composition according to an embodimentincludes the oligomer within the specified range above, it may haveappropriate hydrolysis and appropriate biodegradability. In particular,the biodegradable resin composition according to an embodiment includesthe first oligomer, the second oligomer, the third oligomer and thefourth oligomer within the specified range above, it may haveappropriate hydrolysis and appropriate biodegradability.

The oligomer may adjust the biodegradability of the biodegradablepolyester resin composition according to an embodiment as describedabove. Accordingly, the biodegradable polyester resin compositionaccording to an embodiment may have appropriate hydrolysis andappropriate biodegradability.

Since the biodegradable polyester resin composition according to anembodiment includes an oligomer having the above-describedcharacteristics, it may have a low initial hydrolysis degree, a highlater hydrolysis degree and a high later biodegradability.

Accordingly, the biodegradable polyester resin composition according toan embodiment may be efficiently applied to a film for packaging and thelike. That is, a film made of the biodegradable polyester resincomposition according to an embodiment may be used for general purposessuch as packaging. Here, since the biodegradable polyester resincomposition according to an embodiment has a low initial hydrolysisdegree, the biodegradable polyester film may maintain mechanical andchemical properties to a certain extent or more within a period ofnormal use by a user.

In addition, since the biodegradable polyester resin compositionaccording to an embodiment includes an oligomer having theabove-described characteristics, it may have a higher hydrolysis degree.Accordingly, a film made of the biodegradable polyester resincomposition according to an embodiment may be degraded when discardedafter use.

In addition, the biodegradable polyester resin composition according toan embodiment includes an oligomer having the above-describedcharacteristics, decomposition by ambient moisture and decomposition bymicroorganisms may be complemented each other. Accordingly, thebiodegradable polyester resin composition according to an embodiment mayhave a high biodegradability degree while having a low initialhydrolysis degree.

In addition, since the biodegradable polyester resin compositionaccording to an embodiment includes an oligomer having theabove-described characteristics, it may have a biodegradability peraliphatic carboxylic acid of about 1.5 or more. That is, thebiodegradable polyester resin composition according to an embodiment hasa high biodegradability degree while having a low aliphatic carboxylicacid content. Accordingly, since the biodegradable polyester resincomposition according to an embodiment has a relatively high aromaticcarboxylic acid content, it may have a high biodegradability in a laterperiod while having a high hydrolysis resistance in an initial period.

The biodegradable polyester resin composition according to an embodimentmay maintain mechanical and chemical properties above a certain levelduring the period of use by a user. At the same time, since thebiodegradable polyester resin composition according to an embodiment hasa high later hydrolysis degree, it may be degraded in rivers or sea.That is, the biodegradable polyester resin composition according to anembodiment may solve environmental problems such as plastic pollution inthe ocean.

The oligomer may appropriately control the hydrolysis degree of thebiodegradable polyester resin composition according to an embodiment.The oligomer may be a hydrolysis regulator that appropriately controlsthe hydrolysis degree of the biodegradable polyester resin compositionaccording to an embodiment.

In addition, the oligomer may appropriately control the biodegradabilityof the biodegradable polyester resin composition according to anembodiment. The oligomer may be a biodegradation regulator thatappropriately controls the biodegradability of the biodegradablepolyester resin composition according to an embodiment.

The biodegradable polyester resin composition according to an embodimentmay include a heat stabilizer. The heat stabilizer may be aphosphorus-based heat stabilizer.

The heat stabilizer may be at least one selected from the groupconsisting of an amine-based high-temperature heat stabilizer such astetraethylenepentamine, triethylphosphonoacetate, phosphoric acid,phosphorous acid, polyphosphric acid, trimethyl phosphate (TMP),triethyl phosphate, trimethyl phosphine, triphenyl phosphine and thelike.

In addition, the heat stabilizer may be an antioxidant having anantioxidant function.

The content of the heat stabilizer may range from about 3000 ppm or lessbased on the total weight of the biodegradable polyester resin. Thecontent of the heat stabilizer may be, for example, 10 ppm to 3,000 ppm,20 ppm to 2,000 ppm, 20 ppm to 1,500 ppm or 20 ppm to 1,000 ppm based onthe total weight of the biodegradable polyester resin. When the contentof the heat stabilizer satisfies the range, the deterioration of thepolymer due to high temperature during the reaction process may becontrolled so that terminal groups of the polymer may be reduced and thecolor may be improved. In addition, the heat stabilizer may suppress theactivation of a titanium-based catalyst, thereby controlling a reactionrate.

The biodegradable polyester resin composition according to an embodimentmay include an elongation improver. Examples of the elongation improverinclude oil such as paraffin oil, naphthenic oil, or aromatic oil, oradipate such as dibutyl adipate, diethylhexyl adipate, dioctyl adipate,or diisopropyl adipate.

The elongation improver may be included in the biodegradable polyesterresin composition according to an embodiment in a content ranging fromabout 0.001 parts by weight to about 1 part by weight based on 100 partsby weight of the biodegradable polyester resin. The elongation improvermay be included in a content ranging from about 0.01 parts by weight toabout 1 part by weight based on 100 parts by weight of the biodegradablepolyester resin in the biodegradable polyester resin compositionaccording to an embodiment.

Since the elongation improver is included within the specified rangeabove, the biodegradable polyester resin composition according to anembodiment may have improved mechanical properties.

The biodegradable polyester resin composition according to an embodimentmay include an inorganic filler. The inorganic filler may be at leastone selected from the group consisting of calcium sulfate, bariumsulfate, talc, talc powder, bentonite, kaolinite, chalk powder, calciumcarbonate, graphite, gypsum, electrically conductive carbon black,calcium chloride, iron oxide, aluminum oxide, potassium oxide, dolomite,silicon dioxide, wollastonite, titanium dioxide, silicate, mica, glassfiber, mineral fiber, and the like.

In particle diameter distribution obtained by laser diffraction for theinorganic filler, a cumulative 50% particle size (D₅₀) based on volumemay range from about 100 μm or less, about 85 μm or less, about 70 μm orless, about 50 μm or less, about 25 μm or less, about 10 μm or less,about 5 μm or less, about 3 μm or less or about 1 μm or less.

In addition, the specific surface area of the inorganic filler may rangefrom about 100 m²/g or more. For example, the specific surface area ofthe inorganic filler may range from about 100 m²/g or more, about 105m²/g or more, or about 110 m²/g or more.

The inorganic filler may be included in the biodegradable polyesterresin composition according to an embodiment in a content ranging fromabout 3 parts by weight to about 50 parts by weight based on 100 partsby weight of the biodegradable polyester resin. The inorganic filler maybe included in the biodegradable polyester resin composition accordingto an embodiment in a content ranging from about 5 parts by weight toabout 30 parts by weight based on 100 parts by weight of thebiodegradable polyester resin.

The inorganic filler may be included in a content ranging from about3,000 ppm or less based on the total weight of the biodegradablepolyester resin composition according to an embodiment. For example, thecontent of the inorganic filler may range from about 3,000 ppm or less,about 1,500 ppm or less, about 1,200 ppm or less, about 800 ppm or lessor about 600 ppm or less, particularly about 50 ppm or more, about 100ppm or more, about 130 ppm or more, about 150 ppm or more or about 180ppm or more based on the total weight of the biodegradable polyesterresin composition according to an embodiment.

Since the biodegradable polyester resin composition according to anembodiment includes the inorganic filler within the specified rangeabove, the biodegradable polyester resin composition according to anembodiment may have mechanical properties, appropriate UV resistance, anappropriate biodegradation rate and an appropriate hydrolysis rate.

The biodegradable polyester resin composition according to an embodimentmay further include a heterogeneous biodegradable resin. Thebiodegradable polyester resin composition according to an embodiment maybe a composite resin composition including two or more types of resins,a filler and an additive.

The heterogeneous biodegradable resin may be at least one selected fromthe group consisting of polybutylene azelate terephthalate (PBAzT),polybutylene sebacate terephthalate (PBSeT) and polybutylene succinateterephthalate (PBST), polyhydroxyalkanoate (PHA) or polylactic acid(PLA).

The heterogeneous biodegradable resin may be included in thebiodegradable polyester resin composition according to an embodiment ina content ranging from about 10 parts by weight to about 100 parts byweight based on 100 parts by weight of the biodegradable polyesterresin. The heterogeneous biodegradable resin may be included in thebiodegradable polyester resin composition according to an embodiment ina content ranging from about 10 parts by weight to about 60 parts byweight based on 100 parts by weight of the biodegradable polyesterresin. The heterogeneous biodegradable resin may be included in thebiodegradable polyester resin composition according to an embodiment ina content ranging from about 20 parts by weight to about 50 parts byweight based on 100 parts by weight of the biodegradable polyesterresin.

The heterogeneous biodegradable resin may supplement the mechanical,optical and chemical properties of the biodegradable polyester resin.Since the biodegradable polyester resin composition according to anembodiment includes the heterogeneous biodegradable resin in thecontent, the biodegradable polyester resin composition according to anembodiment may have mechanical properties, appropriate UV resistance, anappropriate biodegradation rate and an appropriate hydrolysis rate.

In addition, the number of carboxyl terminal groups of the biodegradablepolyester resin composition according to an embodiment may range fromabout 50 eq/ton or less. For example, the number of the carboxylterminal groups of the biodegradable polyester resin according to anembodiment may range from about 50 eq/ton or less, about 48 eq/ton orless, about eq/ton or less or about 42 eq/ton or less. When the numberof the carboxyl terminal groups is adjusted to the above range,deterioration may be prevented and improved mechanical properties may beachieved when the biodegradable polyester resin composition according toan embodiment is extruded to form a molded article.

In addition, the intrinsic viscosity (IV) of the biodegradable polyesterresin composition according to an embodiment may range from about 0.9dl/g or more. The intrinsic viscosity of the biodegradable polyesterresin composition according to an embodiment may range from about 0.95dl/g or more, about 1.0 dl/g or more, about 1.1 dl/g or more, about 1.2dl/g or more or about 1.3 dl/g or more. The intrinsic viscosity of thebiodegradable polyester resin composition according to an embodiment mayrange from about 0.95 dl/g to about 1.7 dl/g. The intrinsic viscosity ofthe biodegradable polyester resin composition according to an embodimentmay range from about 1.3 dl/g to about 1.7 dl/g. The intrinsic viscosityof the biodegradable polyester resin composition according to anembodiment may range from about 1.4 dl/g to about 1.7 dl/g.

A process of preparing the biodegradable polyester resin compositionaccording to an embodiment is as follows.

Referring to FIG. 1 , an apparatus for producing the biodegradablepolyester resin includes a slurry stirrer 100, an esterification part200, a polycondensation reaction part 300, a post-treatment part 400, afirst recovery part 510 and a second recovery part 520.

A method of preparing the biodegradable polyester resin includes anoperation of preparing a slurry including the diol and the aromaticdicarboxylic acid.

The operation of preparing a slurry includes an operation of mixing andprocessing the diol and the aromatic dicarboxylic acid. That is, theoperation of preparing a slurry is a pretreatment before anesterification and may be an operation of mixing the diol and thearomatic dicarboxylic acid and slurrying the mixture. Here, the diol mayinclude a biomass-based diol component.

The temperature of the slurry of the diol and the aromatic dicarboxylicacid may range from about 5° C. to about 15° C. higher than the meltingpoint of the diol. For example, when the diol is 1,4-butanediol, thetemperature of the slurry may range from about 35° C. to about 45° C.

The diol and the aromatic dicarboxylic acid are fed into and stirred inthe slurry stirrer 100, thereby preparing the slurry.

By mixing, pre-treating, and slurrying the diol and the aromaticdicarboxylic acid, the diol and the aromatic dicarboxylic acid may beuniformly reacted and the speed of an esterification may be effectivelyaccelerated, thereby increasing reaction efficiency.

In particular, when an aromatic dicarboxylic acid, such as terephthalicacid, has complete crystallinity and is in powder form, it may bedifficult to cause a homogeneous reaction due to very low solubility inthe diol. Therefore, the slurrying pretreatment process may play a veryimportant role in providing a biodegradable polyester resin, sheet, filmand molded article having improved properties according to an embodimentof the present disclosure and improving reaction efficiency.

When the aromatic dicarboxylic acid is terephthalic acid, theterephthalic acid is a white crystal that has complete crystallinity andsublimes at around 300° C. under atmospheric pressure without a meltingpoint. In addition, the terephthalic acid has very low solubility in thediol, making it difficult for a homogeneous reaction to occur.Accordingly, when a pretreatment process is performed before anesterification, a uniform reaction may be induced by increasing thesurface area for reacting with a diol in a solid matrix of terephthalicacid.

In addition, when the aromatic dicarboxylic acid is dimethylterephthalate, the dimethyl terephthalate may be made into a moltenstate at about 142° C. to 170° C. by the pretreatment process andreacted with the diol, so that an esterification can be proceeded fasterand more efficiently.

Meanwhile, in the pretreatment step of preparing the slurry, thestructure and properties of the biodegradable polyester resin may varydepending on the particle size, particle size distribution, pretreatmentreaction conditions, and the like of the aromatic dicarboxylic acid.

For example, the aromatic dicarboxylic acid may include terephthalicacid, and the terephthalic acid may have an average particle diameter(D50) of 10 μm to 400 μm measured by a particle size analyzer MicrotracS3500 in a particle size distribution (PSD), and a standard deviation ofthe average particle diameter (D50) may be 100 or less. The standarddeviation means the square root of the variance. The average particlediameter (D50) of the terephthalic acid may be for example 20 μm to 200μm, for example 30 μm to 180 μm, or for example 100 μm to 160 μm. Whenthe average particle diameter (D50) of the terephthalic acid satisfiesthe range, it may be more advantageous in terms of the solubilityimprovement of the diol and the reaction rate.

In the pretreatment process, the diol and the aromatic dicarboxylic acidmay be mixed and fed into the slurry stirrer 100 (tank).

The slurry stirrer 100 may be provided with, for example, an anchor-typebottom, a height to the agitator of 20 mm or more, and two or morerotary blades, which may be more advantageous to achieve an efficientstirring effect.

For example, the slurry stirrer 100 has a height of 20 mm or more to theagitator, i.e., the reactor and the bottom of the agitator may be almostattached to each other. In this case, a slurry may be obtained withoutprecipitation. If the shape and rotary blades of the agitator do notsatisfy the conditions, the aromatic dicarboxylic acid may precipitateto the bottom when the diol and the aromatic dicarboxylic acid areinitially mixed. In this case, phase separation may occur.

The pretreatment step of preparing the slurry may include a step ofmixing the diol and the aromatic dicarboxylic acid and stirring themixture about 50 rpm to about 200 rpm at about 30° C. to about 100° C.for 10 minutes or more, for example 10 minutes to 200 minutes.

The diol may have characteristics as described above.

The diol may be added at one time or intermittently. For example, thediol may be added intermittently when mixing with an aromaticdicarboxylic acid and when mixing with an aliphatic dicarboxylic acid.

The aromatic dicarboxylic acid may have characteristics as describedabove.

In the pretreatment of preparing the slurry, a molar ratio of the diolto the aromatic dicarboxylic acid may range from about 0.8:1 to about2:1. In the pretreatment of preparing the slurry, a molar ratio of thediol to the aromatic dicarboxylic acid may range from about 1.1:1 toabout 1.5:1. In the pretreatment of preparing the slurry, a molar ratioof the diol to the aromatic dicarboxylic acid may range from about 1.2:1to about 1.5:1.

When the diol is added in a larger amount than the aromatic dicarboxylicacid, the aromatic dicarboxylic acid may be dispersed.

In addition, an additive may be added to the slurry. The nanocelluloseand/or the metal salt may be added in the form of a dispersion orsolution to the slurry.

In the method of preparing the biodegradable polyester resin, aprepolymer is obtained by esterification using a slurry obtained bymixing and pretreating a diol and an aromatic dicarboxylic acid, and theprepolymer is condensation-polymerized, so that the desired structureand physical properties of the biodegradable polyester resin accordingto the embodiment of the present disclosure may be efficiently achieved.

The method of preparing the biodegradable polyester resin includes astep of esterifying the slurry and the aliphatic dicarboxylic acid toprepare a prepolymer. The slurry and the aliphatic dicarboxylic acid maybe reacted in the ester reaction part.

In the esterification, the reaction time may be shortened by using theslurry. For example, a slurry obtained from the pretreatment operationmay shorten the reaction time of the esterification by 1.5 times ormore.

The esterification may be performed at least twice. A prepolymer to beadded to a condensation polymerization process may be formed by theesterification.

In an embodiment, the esterification may be performed at once afteradding an aliphatic dicarboxylic acid, or a diol and an aliphaticdicarboxylic acid to the slurry. That is, the esterification may proceedwhen the slurry is fed into the esterification part 200 and thealiphatic dicarboxylic acid alone or the aliphatic dicarboxylic acid andthe diol are fed into the esterification part 200.

The diol and the aliphatic dicarboxylic acid may be added in the form ofa slurry to a slurry including the aromatic dicarboxylic acid.

In the slurry of the diol and the aliphatic dicarboxylic acid, theaverage particle diameter (D50) of the aliphatic dicarboxylic acid mayrange from about 50 μm to about 150 μm.

In the slurry of the diol and the aliphatic dicarboxylic acid, theaverage particle diameter (D50) of the aliphatic dicarboxylic acid mayrange from about 60 μm to about 120 μm.

In the esterification, the total number of moles of the diols introducedmay range from about 1.0 to about 1.8 relative to the total number ofmoles of the aromatic dicarboxylic acid and the aliphatic dicarboxylicacid. In the esterification, the total number of moles of the diolsintroduced may range from about 1.1 to about 1.6 relative to the totalnumber of moles of the aromatic dicarboxylic acid and the aliphaticdicarboxylic acid.

In addition, the temperature of the slurry of the diol and the aliphaticdicarboxylic acid may range from about 5° C. to about 15° C. higher thanthe melting point of the diol.

In addition, various additives such as the nanocellulose may also beadded to the slurry of the diol and the aliphatic dicarboxylic acid.

The esterification may be performed at about 250° C. or less for about0.5 hours to about 6 hours. Specifically, the esterification may beperformed at about 180° C. to about 250° C., about 185° C. to about 240°C. or about 200° C. to about 240° C. under normal pressure or reducedpressure until the theoretical amount of water as a by-product reaches95%. For example, the esterification may be performed for 0.5 hours to5.5 hours, 0.5 hours to 4.5 hours or 1 hour to 4 hours, but is notlimited thereto.

In the esterification, the total number of moles of the diols introducedmay be 1.0 to about 1.8 relative to the total number of moles of thearomatic dicarboxylic acid and the aliphatic dicarboxylic acid about. Inthe esterification, the total number of moles of the diols introducedmay range from about 1.1 to about 1.6 relative to the total number ofmoles of the aromatic dicarboxylic acid and the aliphatic dicarboxylicacid.

In addition, the temperature of the slurry of the diol and the aliphaticdicarboxylic acid may range from about 5° C. to about 15° C. higher thanthe melting point of the diol.

In addition, various additives such as the nanocellulose may also beadded to the slurry of the diol and the aliphatic dicarboxylic acid.

In an embodiment, first esterification may proceed with the slurryitself or after adding the diol to the slurry. In addition, after thefirst esterification, the aliphatic dicarboxylic acid or a mixture ofthe aliphatic dicarboxylic acid and the diol may be fed into the esterreaction part, and second esterification may proceed together with thefirst esterification product.

The first esterification may be performed at 250° C. or less for 0.25hours to 4 hours. Specifically, the first esterification may beperformed at 180° C. to 250° C., 185° C. to 240° C. or 200° C. to 240°C. under normal pressure or reduced pressure until the theoreticalamount of water as a by-product reaches 95%. For example, the firstesterification may be performed for 0.25 hours to 4 hours, 0.25 hours to3.5 hours or 1.5 hours to 3 hours, but is not limited thereto.

The second esterification may be performed at about 250° C. or less for0.25 hours to 3.5 hours. Specifically, the second esterification may beperformed at 180° C. to 250° C., 185° C. to 240° C. or 200° C. to 240°C. under normal pressure or reduced pressure until the theoreticalamount of water as a by-product reaches 95%. For example, the secondesterification may be performed for 0.5 hours to 3 hours, 1 hour to 2.5hours or 1.5 hours to 3 hours, but is not limited thereto.

In the first esterification and the second esterification, a ratio ofthe number of the first blocks to the number of the second blocks andthe like may be controlled by respectively adjusting the reactiontemperature and the reaction time. In addition, the esterification isdivided into the first esterification and the second esterification, theentire esterification may be precisely controlled. Accordingly, when theesterification is divisionally performed, the reaction stability andreaction uniformity of the esterification may be improved.

After the second esterification is completed, third esterification maybe performed. Here, a monomer composition including at least one of thediol, the aromatic dicarboxylic acid and the aliphatic dicarboxylic acidmay be added to the second esterification product, and the thirdesterification may be performed.

The monomer composition may be added in a content ranging from about 0.5parts by weight to about 5 parts by weight based on 100 parts by weightof the second esterification product to the second esterificationproduct.

In addition, in the monomer composition, a molar ratio of the aromaticdicarboxylic acid to the aliphatic dicarboxylic acid may range fromabout 1:1 to about 1:3. In the monomer composition, a molar ratio of thearomatic dicarboxylic acid to the aliphatic dicarboxylic acid may rangefrom about 1:1.3 to about 1:3.

In addition, in the monomer composition, a molar ratio of the diol toall the dicarboxylic acids may range from about 0.8:1 to 1:1.2.

The third esterification may be performed at about 250° C. or less for0.1 hours to 0.5 hours. Specifically, the third esterification may beperformed at 180° C. to 250° C., 185° C. to 240° C. or 200° C. to 240°C. under normal pressure or reduced pressure. For example, the thirdesterification may be performed for 5 minutes to 40 minutes, 10 minutesto 30 minutes or 10 minutes to 20 minutes, but is not limited thereto.

A prepolymer may be formed by the third esterification.

When using the monomer composition and performing the thirdesterification under the above-described conditions, the content of theoligomer may be appropriately controlled.

Alternatively, the oligomer may be separately prepared and added to thesecond esterification product to produce the prepolymer.

In the third esterification, the second esterification product may notbe used. That is, the third esterification may be performed by themonomer composition and other additives such as a catalyst. Next, thesecond esterification product and the third esterification product aremixed to produce the prepolymer. Here, the third esterification productis mixed with the second esterification product in a content rangingfrom about 0.1 parts by weight to about 5 parts by weight based on 100parts by weight of the second esterification product, thereby producingthe prepolymer.

The number average molecular weight of the prepolymer may range fromabout 500 to about 10000 g/mol. For example, the number averagemolecular weight of the prepolymer may range from about 500 to about8500 g/mol, about 500 to about 8000 g/mol, about 500 to about 7000g/mol, about 500 g/mol to about 5000 g/mol, or about 800 g/mol to about4000 g/mol. When the number average molecular weight of the prepolymersatisfies the range, the molecular weight of a polymer in apolycondensation reaction may be efficiently increased.

The number average molecular weight may be measured using gel permeationchromatography (GPC). Specifically, data obtained by gel permeationchromatography includes various items such as Mn, Mw and Mp. Thereamong,the molecular weight may be measured based on the number averagemolecular weight (Mn).

The reinforcing material, the branching agent, the polycarbonate diol,the polyether polyol or the metal salt may be added together with theslurry before the esterification. The reinforcing material, thebranching agent, the polycarbonate diol, the polyether polyol and/or themetal salt may be fed into an esterification part 200 in the middle ofthe esterification. The reinforcing material, the branching agent, thepolycarbonate diol, the polyether polyol and/or the metal salt may beadded to the esterification product after the esterification. Inaddition, the reinforcing material, the branching agent, thepolycarbonate diol, the polyether polyol and/or the metal salt may beadded together with the aliphatic dicarboxylic acid. In addition, thereinforcing material, the branching agent, the polycarbonate diol, thepolyether polyol and/or the metal salt may be fed into theesterification part 200 after the first esterification and before thesecond esterification.

Since the reinforcing material and/or the metal salt is added during theesterification, the reinforcing material and/or the metal salt may beuniformly dispersed in the biodegradable polyester resin.

The reinforcing material may have the above-described characteristics.In particular, the nanocellulose may be used as the reinforcingmaterial.

The nanocellulose may be pre-treated by a bead mill, pre-treated byultrasonic waves, or pre-treated by high-speed dispersion at about 1000rpm to about 1500 rpm before being introduced. Specifically, thenano-cellulose may be water-dispersed nano-cellulose pre-treated with abead mill or pre-treated with ultrasonic waves.

First, the bead mill pretreatment may be performed with a vertical millor horizontal mill as a wet milling device. With the horizontal mill,the amount of beads that can be filled into a chamber is greater, theuneven wear of the machine is reduced, the wear of the beads is reduced,and maintenance is easier.

The bead mill pretreatment may be performed using one or more bead typesselected from the group consisting of zirconium, zircon, zirconia,quartz and aluminum oxide.

Specifically, the bead mill pretreatment may be performed using beadshaving a diameter of about 0.3 mm to about 1 mm. For example, thediameter of the beads may range from about 0.3 mm to about 0.9 mm, about0.4 mm to about 0.8 mm, about 0.45 mm to about 0.7 mm or about 0.45 mmto about 0.6 mm.

When the diameter of the beads satisfies the range, the dispersibilityof nanocellulose may be further improved. When the diameter of the beadsexceeds the range, the average particle diameter and average particledeviation of nanocellulose increase, resulting in low dispersibility.

In addition, in the bead mill pretreatment, beads with a higher specificgravity than that of nanocellulose may be used. For example, the beadsmay be one or more selected from the group consisting of zirconium,zircon, zirconia, quartz and aluminum oxide which have a higher specificgravity than water-dispersed nanocellulose, and zirconium beads having aspecific gravity four times or higher than the water-dispersednanocellulose are preferred, without being not limited thereto.

In addition, the ultrasonic pretreatment is a method of physicallyclosing or pulverizing nanoparticles with waves generated by emitting 20kHz ultrasound into a solution.

The ultrasonic pretreatment may be performed for less than 30 minutes atan output of 30000 J/s or less. For example, the ultrasonic pretreatmentmay be performed at an output of 25000 J/s or less or 22000 J/s or lessfor 25 minutes or less, 20 minutes or less or 18 minutes or less. Whenthe output and the execution time satisfy the above ranges, the effect,i.e., the improvement of dispersibility, of the ultrasonic pretreatmentmay be maximized. When the output exceeds the above range, thenanoparticles may rather re-agglomerate and the dispersibility may belowered.

The nanocellulose according to an embodiment may be pre-treated with abead mill or pre-treated with ultrasonic waves. Alternatively, thenanocellulose according to an embodiment may be pre-treated with a beadmill and pre-treated with ultrasonic waves. Here, it is preferred toperform ultrasonic pretreatment after pre-treating with a bead mill interms of improving dispersibility by preventing re-agglomeration.

The nanocellulose according to an embodiment may be pre-treated with abead mill or pre-treated with ultrasonic waves. Alternatively, thenanocellulose according to an embodiment may be pre-treated with a beadmill and pre-treated with ultrasonic waves. Here, it is preferred toperform ultrasonic pretreatment after pretreatment with a bead mill interms of improving dispersibility by preventing reagglomeration.

Since the nanocellulose includes an ion-bonded metal, it has very highdispersibility in water. In addition, an aqueous dispersion having avery high dispersion of the nanocellulose may be obtained by the beadmill pretreatment and/or the ultrasonic pretreatment. In the aqueousnanocellulose dispersion, the content of the nanocellulose may rangefrom about 1 wt % to about 50 wt %.

In the esterification, a titanium-based catalyst and/or agermanium-based catalyst may be used. Specifically, the titanium-basedcatalyst and/or the germanium-based catalyst may be added to the slurry,and the esterification may be performed.

In addition, the titanium-based catalyst and/or the germanium-basedcatalyst may be added to the slurry before the first esterification, andthe titanium-based catalyst and/or the germanium-based catalyst may befurther added to the product of the first esterification.

The biodegradable polyester resin may include one or more titanium-basedcatalysts selected from the group consisting of titanium isopropoxide,antimony trioxide, dibutyltin oxide, tetrapropyl titanate, tetrabutyltitanate, tetraisopropyl titanate, antimonia acetate, calcium acetateand magnesium acetate, or one or more germanium-based catalysts selectedfrom the group consisting of germanium oxide, germanium methoxide,germanium ethoxide, tetramethyl germanium, tetraethyl germanium andgermanium sulfide.

In addition, the content of the catalyst may range from about 50 ppm to2000 ppm based on a total weight of a diol, an aromatic dicarboxylicacid, and an aliphatic dicarboxylic acid. For example, about 60 ppm toabout 1600 ppm, about 70 ppm to about 1400 ppm, about 80 ppm to about1200 ppm or about 100 ppm to about 1100 ppm of titanium-based catalystor germanium-based catalyst may be included. When the content of thecatalyst satisfies the range, the physical properties may be furtherimproved.

In addition, the heat stabilizer may be added together with the slurrybefore the esterification. The heat stabilizer may be fed into theesterification part 200 in the middle of the esterification. The heatstabilizer may be added to the esterification product after theesterification. In addition, the heat stabilizer may be added togetherwith the aliphatic dicarboxylic acid. In addition, the heat stabilizermay be fed into the esterification part 200 after the firstesterification and before the second esterification.

The characteristics of the heat stabilizer may be as described above.

The content of the heat stabilizer may be 3,000 ppm or less based on atotal weight of a diol, an aromatic dicarboxylic acid, and an aliphaticdicarboxylic acid. Specifically, the content of the heat stabilizer maybe, for example, 10 ppm to 3,000 ppm, 20 ppm to 2,000 ppm, ppm to 1,500ppm or 20 ppm to 1,000 ppm based on a total weight of a diol, anaromatic dicarboxylic acid, and an aliphatic dicarboxylic acid. When thecontent of the heat stabilizer satisfies the range, the deterioration ofthe polymer due to high temperature during the reaction process may becontrolled, the terminal groups of the polymer may be reduced and thecolor may be improved.

After completion of the esterification, one or more selected from thegroup consisting of an additive such as silica, potassium or magnesiumand a color-correcting agent such as cobalt acetate may be further addedto the esterification product. That is, after completion of theesterification, the additive and/or the color-correcting agent may beadded and stabilized, and then a polycondensation reaction may beperformed. The additive and/or the color-correcting agent may be addedafter completion of the esterification, and may be fed into thepolycondensation reaction part 300 together with the prepolymer.Accordingly, the additive and/or the color-correcting agent may beuniformly dispersed in the biodegradable polyester resin.

In addition, after completion of the esterification, the inorganicfiller may be added to the esterification product. That is, theinorganic filler is added and stabilized after completion of theesterification, and then the polycondensation reaction may be performed.The characteristics of the inorganic filler are as described above. Theinorganic filler may be fed into the polycondensation reaction part 300together with the prepolymer, and the condensation polymerizationprocess may be performed. Accordingly, the inorganic filler may beuniformly dispersed in the biodegradable polyester resin.

In addition, the first recovery part 510 recovers by-products such aswater from the esterification part 200. The first recovery part 510 mayrecover by-products generated from the esterification by applying vacuumpressure to the esterification part 200 or proceeding with reflux.

The method of preparing the biodegradable polyester resin includes astep of polycondensing the prepolymer. The polycondensation reaction maybe performed as follows.

The prepolymer is fed into the polycondensation reaction part 300. Inaddition, at least one of the reinforcing material, the heat stabilizer,the color-correcting agent, the inorganic filler, the metal salt andother additives may be fed into the polycondensation reaction part 300together with the prepolymer.

In addition, the prepolymer and the oligomer composition may be added tothe polycondensation reaction part, and a polycondensation reaction ofthe prepolymer and the oligomer may be performed.

The oligomer composition may be prepared by the following method.

The oligomer composition may be prepared by esterification of the diol,the aromatic dicarboxylic acid and the aliphatic dicarboxylic acid.Here, the oligomer composition may be prepared to include an oligomerhaving a molecular weight of 400 to 1300 as a main component.

The temperature of the esterification for preparing the oligomercomposition may range from about 200° C. to about 250° C. In addition,the esterification time for preparing the oligomer composition may rangefrom about 5 minutes to about 20 minutes.

In addition, the content of the oligomer composition added to thepolycondensation reaction may range from about 0.5 wt % to about 10 wt %based on the total weight of the materials added to the polycondensationreaction. The content of the oligomer composition added to thepolycondensation reaction may range from about 1 wt % to about 7 wt %based on the total weight of the materials added to the polycondensationreaction.

Since the characteristics and content of the oligomer composition are asdescribed above, the biodegradable polyester resin composition accordingto an embodiment may include the oligomer having a molecular weight of400 to 1300 in an appropriate content.

Next, the polycondensation reaction may be performed at about 180° C. toabout 280° C. and about 10 Torr or less for about 1 hour to about 5hours. For example, the polycondensation reaction may be performed atabout 190° C. to about 270° C., about 210° C. to about 260° C. or about230° C. to about 255° C., may be performed at about 0.9 Torr or less,about 0.7 Torr or less, about 0.2 Torr to about 10 Torr, about 0.2 Torrto about 0.9 Torr or about 0.2 Torr to about 0.6 Torr, and may beperformed for about 1.5 hours to about 5 hours, about 2 hours to about 5hours or about 2.5 hours to about 4.5 hours.

In addition, the polycondensation reaction may include firstpolycondensation and second polycondensation.

For example, the first polycondensation may be performed at about 260°C. or less, about 250° C. or less, about 215° C. to about 250° C., about215° C. to about 245° C. or about 230° C. to about 245° C. under about 1torr to about 200 torr, about 2 Torr to about 100 torr, about 4 Torr toabout 50 torr, about 5 Torr to about 45 Torr or about 8 Torr to about 32Torr for about 0.5 hours to about 3.5 hours, about 0.5 hours to about3.0 hours or about 0.5 hours to about 2.8 hours.

In addition, the second polycondensation may be performed at about 220°C. to about 265° C., about 230° C. to about 260° C. or about 235° C. toabout 255° C. under about 1 torr or less, about 0.8 Torr or less, about0.6 Torr or less, about 0.1 Torr to about 1 torr, about 0.2 Torr toabout 0.8 Torr or about 0.2 Torr to about 0.6 Torr for about 0.5 hoursto about 4 hours, about 1 hour to about 3.5 hours or about 1.5 hours toabout 3.5 hours.

In addition, before the polycondensation reaction, a titanium-basedcatalyst or a germanium-based catalyst may be further added to theprepolymer. In addition, before the polycondensation reaction, one ormore selected from the group consisting of an additive such as silica,potassium or magnesium; an amine-based stabilizer such as trimethylphosphate, triphenyl phosphate, trimethyl phosphine, phosphoric acid,phosphorous acid, or tetraethylenepentamine; and a polymerizationcatalyst such as antimony trioxide, antimony trioxide or tetrabutyltitanate may be further added to the prepolymer.

The number average molecular weight of the polymer may range from about30000 g/mol or more. For example, the number average molecular weight ofthe polymer may range from about 33000 g/mol or more, about 35000 g/molor more or about 40000 g/mol to about 90000 g/mol. When the numberaverage molecular weight of the polymer satisfies the range, physicalproperties, impact resistance, durability and moldability may be furtherimproved.

In addition, the second recovery part 520 recovers by-products such aswater from the polycondensation reaction part 300. The second recoverypart 520 may apply vacuum pressure to the polycondensation reaction part300, and may recover by-products generated in the polycondensationreaction.

The second recovery part 520 may apply a vacuum pressure of about 0.1Torr to about 1 torr to the inside of the polycondensation reaction part300. The second recovery part 520 may apply a vacuum pressure of about0.1 Torr to about 0.9 Torr to the inside of the polycondensationreaction part 300.

Next, the anti-hydrolysis agent and/or the chain extender are added tothe polymer. Next, the polymer, the anti-hydrolysis agent and the chainextender are uniformly mixed and allowed to stand at about 200° C. toabout 260° C. for about 1 minute to about 15 minutes. Accordingly, thepolymer reacts with the anti-hydrolysis agent and/or the chain extender.

Alternatively, the anti-hydrolysis agent and/or the chain extender maybe fed into the polycondensation reaction part 300 through a staticmixer and reacted with the polymer. A reaction temperature of theanti-hydrolysis agent and/or the chain extender in the polycondensationreaction part 300 may range from about 200° C. to about 260° C. Inaddition, a reaction time of the anti-hydrolysis agent and/or the chainextender in the polycondensation reaction part 300 may range from about1 minute to about 15 minutes.

The anti-hydrolysis agent may have the characteristics described above.

The chain extender may have the characteristics described above.

Accordingly, the biodegradable polyester resin composition according toan embodiment may have appropriate hydrolysis and a highbiodegradability degree.

Next, a pellet may be produced from the polymer.

Specifically, the pellet may be produced by cooling the polymer to about15° C. or less, about 10° C. or less or about 6° C. or less, and thencutting the cooled polymer. Alternatively, the polymer may be cut atabout 40° C. to about 60° C.

The cutting may be performed using any pellet cutting machine used inthe art without limitation, and the pellet may have various shapes. Thepellet cutting method may include an underwater cutting method or astrand cutting method.

The pellet may be subjected to an additional post-treatment process. Thepellet may be fed into the post-treatment part 400, and thepost-treatment process may be performed.

The post-treatment process may be performed in the post-treatment part400. The pellet is fed into the post-treatment part 400. Next, thepost-treatment part 400 may melt and re-extrude the fed pellet byfrictional heat. That is, the post-treatment part 400 may include anextruder such as a twin-screw extruder.

The temperature of the post-treatment process may range from about 230°C. to about 270° C. The temperature of the post-treatment process mayrange from about 230° C. to about 260° C. The temperature of thepost-treatment process may range from about 240° C. to about 265° C. Thetemperature of the post-treatment process may range from about 240° C.to about 260° C.

The post-treatment process time may range from about 30 seconds to about3 minutes. The post-treatment process time may range from about 50seconds to about 2 minutes. The post-treatment process time may rangefrom about 1 minute to about 2 minutes.

Next, A resin extruded by the extruder may be cooled, cut, and processedinto post-treated pellets. That is, the resin extruded from the extrudermay be reprocessed into a pellet through the cutting step describedabove.

Crystallinity of the pellet may be improved in the post-treatmentprocess. In addition, the content of the residue included in the pelletmay be adjusted in the post-treatment process. In particular, thecontent of an oligomer contained in the pellet may be controlled by thepost-treatment process. The amount of residual solvent contained in thepellet may be controlled by the post-treatment process.

Accordingly, the post-treatment process may appropriately control themechanical properties, biodegradability, UV resistance, opticalproperties, or hydrolysis resistance of the biodegradable polyesterresin.

The characteristics and content of the oligomer may depend upon theesterification, the chain extension reaction, the post-treatmentprocess, and the like.

After the pellet is produced, the biodegradable polyester resin may becompounded with the heterogeneous biodegradable resin. In addition, atleast one of the inorganic filler, the light stabilizer, thecolor-correcting agent and the other additives may be compounded withthe biodegradable polyester resin and the heterogeneous biodegradableresin.

The compounding process may be as follows.

The biodegradable polyester resin and the heterogeneous biodegradableresin are mixed with at least one of the inorganic filler, the heatstabilizer, the color-correcting agent, the metal salt or the otheradditives and fed into an extruder. The mixed biodegradable polyesterresin composition is melted and mixed at about 120° C. to about 260° C.in the extruder. Next, the melt-mixed biodegradable polyester resincomposition is extruded, cooled, cut, and re-pelletized. By thisprocess, the biodegradable polyester resin composition according to anembodiment may be prepared by combining it with the heterogeneousbiodegradable resin.

Alternatively, the inorganic filler, the heat stabilizer, thecolor-correcting agent, the metal salt and the other additives may beadded in the middle of the process of polymerizing the biodegradablepolyester resin.

By the biodegradable polyester resin according to an embodiment, abiodegradable polyester film may be prepared.

The thickness of the biodegradable polyester film may range from about 5μm to about 300 μm. For example, the thickness of the biodegradablepolyester film may range from about 5 μm to about 180 μm, about 5 μm toabout 160 μm, about 10 μm to about 150 μm, about 15 μm to about 130 μm,about 20 μm to about 100 μm, about 25 μm to about 80 μm or about 25 μmto about 60 μm.

The biodegradable polyester film according to an embodiment may havesubstantially the same hydrolysis degree and biodegradability as thebiodegradable polyester resin composition described above.

Meanwhile, the biodegradable polyester film may be prepared using thebiodegradable polyester resin or a biodegradable polyester resin pellet.

Specifically, the method of preparing the biodegradable polyester filmmay include an operation of preparing a biodegradable resin compositionaccording to an example and an operation of drying and melt extrudingthe biodegradable resin composition.

In the operation of drying and melt extruding the biodegradable resincomposition, the drying may be performed at about 60° C. to about 100°C. for about 2 hours to about 12 hours. Specifically, the drying may beperformed at about 65° C. to about 95° C., about 70° C. to about 90° C.or about 75° C. to about 85° C. for about 3 hours to about 12 hours orabout 4 hours to about 10 hours. When the drying conditions of thepellet satisfy the ranges, the quality of a produced biodegradablepolyester film or molded article may be further improved.

In the drying and melt extruding operation, the melt extruding may beperformed at about 270° C. or less. For example, the melt extruding maybe performed at about 265° C. or less, about 260° C. or less, about 255°C. or less, about 150° C. to about 270° C., about 150° C. to about 255°C. or about 150° C. to about 240° C. The melt extruding may be performedby a blown film process. The melt extruding may proceed in a T-die.

In addition, the film preparation process may be a calendering process.

Biodegradable Polyester Molded Article

A biodegradable polyester molded article may be manufactured using thebiodegradable polyester resin.

Specifically, the molded article may be manufactured by molding thebiodegradable polyester resin composition in a method, such as extrusionor injection, known in the art, and the molded article may be aninjection-molded article, an extrusion-molded article, a thin-filmmolded product, a blow molding or blow-molded article, 3D filament, aninterior material for construction, or the like, but is not limitedthereto.

For example, the molded article may be in the form of a film or sheetthat can be used as an agricultural mulching film, disposable gloves, adisposable film, a disposable bag, a food packaging material, avolume-rate garbage bag, etc., and may be in the form of a fiber thatcan be used as woven, knitted, non-woven, or a rope. In addition, asshown in FIG. 2 , the molded article may be in the form of a disposablecontainer that can be used as a container for packaging food such as alunch box. In addition, the molded article may be a molded article invarious forms such as a disposable straw, a cutlery (spoon), a foodplate, or a fork.

In particular, since the molded article may be formed from thebiodegradable polyester resin capable of improving physical propertiessuch as shock absorption energy and hardness, in particular, impactresistance and durability, it may exhibit improved properties whenapplied to packaging materials for products stored and transported atlow temperatures, interior materials for automobiles requiringdurability, garbage bags, mulching films, and disposable products.

The physical properties of the biodegradable film and the biodegradablemolded article may be measured in a manner similar to those of thebiodegradable polyester resin composition according to an embodiment.

The biodegradability of the biodegradable polyester resin compositionaccording to an embodiment may be measured by the following method.

To measure the biodegradability, the biodegradable polyester resincomposition according to an embodiment was mixed with compost, and abiodegradation acceleration test was conducted at 60° C. and a relativehumidity 90%. After a certain period, the number average molecularweight of the biodegradable polyester resin composition according to anembodiment was measured using gel permeation chromatography (GPC). Abiodegradability was derived by dividing a difference between an initialnumber average molecular weight and a number average molecular weightafter biodegradation for a certain period by the initial number averagemolecular weight.

The biodegradability may be represented by Equation 1 below:

$\begin{matrix}{{{Biodegradability}(\%)} = {\frac{\begin{matrix}{{{Initial}{number}{average}{molecular}{weight}} -} \\\begin{matrix}{{number}{average}{molecular}} \\{{weight}{after}{biodegradation}}\end{matrix}\end{matrix}}{{Initial}{number}{average}{molecular}{weight}} \times 100}} & \left\lbrack {{Equation}1} \right\rbrack\end{matrix}$

Here, the biodegradable polyester resin composition according to anembodiment is mixed with compost and subjected to a biodegradationacceleration test at 60° C. and a relative humidity of 90% for a certainperiod. An initial number average molecular weight of the biodegradablepolyester resin composition before performing the biodegradabilityacceleration test and a number average molecular weight afterbiodegradation of the biodegradable polyester resin compositionsubjected to the biodegradation acceleration test for a certain periodare measured by gel permeation chromatography (GPC).

The biodegradability was derived by dividing a difference between theinitial number average molecular weight and the number average molecularweight after biodegradation for a certain period by an initial numberaverage molecular weight.

In addition, the compost may include about 40 wt % of pig manure, about15 wt % of chicken manure, about 37 wt % of sawdust, about 5 wt % ofzeolite and about 3 wt % of a microbial agent.

In addition, the compost may be Jisaengto (by-product fertilizer grade 1compost) manufactured by Taeheung F&G.

In addition, when measuring the biodegradability, the biodegradablepolyester resin composition according to an embodiment is manufacturedas a sheet having a thickness of about 300 μm. Next, the manufacturedsheet is cut into a size of about 30 mm×30 mm to produce flakes. Theflakes are mixed with the compost, and the biodegradation accelerationtest is performed.

In the biodegradable polyester resin composition according to anembodiment, a biodegradability after one week may range from about 40%to about 70%. In the biodegradable polyester resin composition accordingto an embodiment, the biodegradability after one week may range fromabout 45% to about 65%. In the biodegradable polyester resin compositionaccording to an embodiment, the biodegradability after one week mayrange from about 47% to about 63%. In the biodegradable polyester resincomposition according to an embodiment, the biodegradability after oneweek may range from about 49% to about 62%.

In the biodegradable polyester resin composition according to anembodiment, the biodegradability after two weeks may range from about50% to about 70%. In the biodegradable polyester resin compositionaccording to an embodiment, the biodegradability after two weeks mayrange from about 55% to about 68%.

In the biodegradable polyester resin composition according to anembodiment, a biodegradability after three weeks may range from about63% to about 75%. In the biodegradable polyester resin compositionaccording to an embodiment, the biodegradability after three weeks mayrange from about 63% to about 73%.

In the biodegradable polyester resin composition according to anembodiment, a biodegradability after four weeks may range from about 73%to about 85%. In the biodegradable polyester resin composition accordingto an embodiment, the biodegradability after four weeks may be 75% to82%.

In the biodegradable polyester resin composition according to anembodiment, a biodegradability after six weeks may range from about 80%to about 90%. In the biodegradable polyester resin composition accordingto an embodiment, the biodegradability after six weeks may range fromabout 82% to about 88%.

In the biodegradable polyester resin composition according to anembodiment, a biodegradability after nine weeks may range from about 85%or more. In the biodegradable polyester resin composition according toan embodiment, the biodegradability after nine weeks may range fromabout 87% or more. In the biodegradable polyester resin compositionaccording to an embodiment, the biodegradability after nine weeks mayrange from about 88% or more. In the biodegradable polyester resincomposition according to an embodiment, the biodegradability after nineweeks may range from about 89% or more. In the biodegradable polyesterresin composition according to an embodiment, the biodegradability afternine weeks may range from about 90% or more.

In the biodegradable polyester resin composition according to anembodiment, a biodegradability increase rate from one week to two weeksmay range from about 4%/week to about 15%/week. In the biodegradablepolyester resin composition according to an embodiment, thebiodegradability increase rate from one week to two weeks may range fromabout 5%/week to about 13%/week.

The hydrolysis degree of the biodegradable polyester resin compositionaccording to an embodiment may be measured by the following method.

To measure the hydrolysis degree, the biodegradable resin compositionaccording to an embodiment is immersed in 80° C. water (100% RH), and ahydrolysis acceleration test is performed. After a certain period, thenumber average molecular weight of the biodegradable polyester resincomposition according to an embodiment was measured using gel permeationchromatography (GPC). A hydrolysis degree was derived by dividing adifference between an initial number average molecular weight and anumber average molecular weight after hydrolysis for a certain period bythe initial number average molecular weight.

The hydrolysis degree may be represented by Equation 2 below:

$\begin{matrix}{{{Hydrolysis}{degree}(\%)} = {\frac{\begin{matrix}{{{Initial}{number}{average}{molecular}{weight}} -} \\\begin{matrix}{{Number}{average}{molecular}} \\{{weight}{after}{hydrolysis}}\end{matrix}\end{matrix}}{{Initial}{number}{average}{molecular}{weight}} \times 100}} & \left\lbrack {{Equation}2} \right\rbrack\end{matrix}$

Here, the biodegradable polyester resin composition according to anembodiment is immersed in 80° C. water, and then subjected to ahydrolysis acceleration test for a certain period. An initial numberaverage molecular weight of the biodegradable polyester resincomposition before performing the hydrolysis acceleration test and anumber average molecular weight after hydrolysis of the biodegradablepolyester resin composition subjected to the hydrolysis accelerationtest for a certain period are measured by gel permeation chromatography(GPC).

The hydrolysis degree was derived by dividing a difference between theinitial number average molecular weight and the number average molecularweight after hydrolysis for a certain period by an initial numberaverage molecular weight.

In addition, when measuring the hydrolysis degree, the biodegradablepolyester resin composition according to an embodiment is manufacturedinto a sheet having a thickness of about 300 μm. Next, the manufacturedsheet is cut into a size of about 30 mm×30 mm to produce flakes. Theflakes may be immersed in the hot water, and the hydrolysis accelerationtest may be performed.

In the biodegradable polyester resin composition according to anembodiment, a hydrolysis degree after one week may range from about 40%to about 65%. In the biodegradable polyester resin composition accordingto an embodiment, the hydrolysis degree after one week may range fromabout 45% to about 63%.

In the biodegradable polyester resin composition according to anembodiment, a hydrolysis degree after two weeks may range from about 80%to about 93%. In the biodegradable polyester resin composition accordingto an embodiment, the hydrolysis degree after two weeks may range fromabout 85% to about 92%.

In the biodegradable polyester resin composition according to anembodiment, a hydrolysis degree after three weeks may range from about90% to about 97%. In the biodegradable polyester resin compositionaccording to an embodiment, a hydrolysis degree after three weeks mayrange from about 91% to about 96%.

In the biodegradable polyester resin composition according to anembodiment, a hydrolysis degree after four weeks may range from about92% to about 99%. In the biodegradable polyester resin compositionaccording to an embodiment, a hydrolysis degree after four weeks mayrange from about 93% to about 97%.

In the biodegradable polyester resin composition according to anembodiment, a hydrolysis degree after six weeks may range from about 94%or more. In the biodegradable polyester resin composition according toan embodiment, a hydrolysis degree after six weeks may range from about95% or more.

In the biodegradable polyester resin composition according to anembodiment, a hydrolysis degree after nine weeks may range from about95% or more. In the biodegradable polyester resin composition accordingto an embodiment, a hydrolysis degree after nine weeks may range fromabout 96% or more.

In the biodegradable polyester resin composition according to anembodiment, a hydrolysis degree increase rate from one week to two weeksmay range from about 25%/week to about 50%/week. In the biodegradablepolyester resin composition according to an embodiment, the hydrolysisdegree increase rate from one week to two weeks may range from about29%/week to about 50%/week. In the biodegradable polyester resincomposition according to an embodiment, the hydrolysis degree increaserate from one week to two weeks may range from about 30%/week to about45%/week.

Since the biodegradable resin composition according to an embodiment hasa hydrolysis degree and hydrolysis degree increase rate within thespecified range above, the biodegradable resin composition according toan embodiment has appropriate durability in daily life and may behydrolyzed when discarded. That is, since the biodegradable resincomposition according to an embodiment has a hydrolysis degree andhydrolysis degree increase rate in an appropriate range, it may havesufficient hydrolysis resistance when used for an appropriate period oftime, such as in disposable packaging. In addition, the biodegradableresin composition according to an embodiment may be degraded byhydrolysis and biodegradation, not only when disposed of in the soil,but also when disposed of in the river or the sea.

In the biodegradable polyester resin composition according to anembodiment, a biodegradability per aliphatic carboxylic acid may rangefrom about 1.5 or more. In addition, the biodegradability per aliphaticcarboxylic acid may range from about 1.65 or more. The biodegradabilityper aliphatic carboxylic acid may range from about 1.75 or more. Thebiodegradability per aliphatic carboxylic acid may range from about 1.8or more. The biodegradability per aliphatic carboxylic acid may rangefrom about 1.85 or more. The biodegradability per aliphatic carboxylicacid may range from about 1.90 or more. A maximum value of thebiodegradability per aliphatic carboxylic acid may range from about 4.

The biodegradability per aliphatic carboxylic acid is obtained bydividing the biodegradability after nine weeks by a ratio of thealiphatic carboxylic acid based on all dicarboxylic acids. Thebiodegradability per aliphatic carboxylic acid is obtained by dividingthe biodegradability after nine weeks by a mol % ratio of the aliphaticcarboxylic acid based on all dicarboxylic acids.

The biodegradability per aliphatic carboxylic acid may be represented byEquation 3 below:

$\begin{matrix}{{{Biodegradability}{per}{aliphatic}{carboxylic}{acid}} = \frac{{Biodegradability}{after}9{weeks}}{\begin{matrix}{{Content}\left( {{mol}\%} \right){of}{aliphatic}{carboxylic}{acid}{in}{all}} \\{{carboxylic}{acids}}\end{matrix}}} & \left\lbrack {{Equation}3} \right\rbrack\end{matrix}$

The biodegradability per the aliphatic carboxylic acid may be in theabove range by appropriately controlling the number of the first blocks,the number of the second blocks, the composition of the biodegradablepolyester resin such as the content of the aliphatic dicarboxylic acidor the content of the aromatic dicarboxylic acid, conditions of theprocess of preparing the biodegradable polyester resin, the reinforcingmaterial, the metal salt, the anti-hydrolysis agent, the chain extender,the oligomer, the heat stabilizer, or the like.

In addition, the acid value of the biodegradable polyester resincomposition according to an embodiment may range from about 0.01 mgKOH/g to about 3 mg KOH/g. The acid value of the biodegradable polyesterresin composition according to an embodiment may range from about 0.1 mgKOH/g to about 2.5 mg KOH/g. The acid value of the biodegradablepolyester resin composition according to an embodiment may range fromabout 0.1 mg KOH/g to about 2.3 mg KOH/g.

Since the biodegradable polyester resin composition according to anembodiment has an acid value within the specified range above, it mayhave hydrolysis and biodegradability characteristics as described above.

In addition, the biodegradable polyester resin composition according toan embodiment may include a nitrogen element. The nitrogen element maybe derived from the metal salt and/or the chain extender. The content ofthe nitrogen element may range from about 0.1 ppm to about 500 ppm basedon the biodegradable polyester resin composition according to anembodiment. The content of the nitrogen element may range from about 1ppm to about 400 ppm based on the biodegradable polyester resincomposition according to an embodiment. The content of the nitrogenelement may range from about 1 ppm to about 300 ppm based on thebiodegradable polyester resin composition according to an embodiment.The content of the nitrogen element may range from about 1 ppm to about100 ppm based on the biodegradable polyester resin composition accordingto an embodiment.

In addition, the biodegradable polyester resin composition according toan embodiment may include a silicon element. The silicon element may bederived from the anti-hydrolysis agent and the like. The content of thesilicon element may range from about 0.1 ppm to about 100 ppm based onthe biodegradable polyester resin composition according to anembodiment. The content of the silicon element may range from about 0.5ppm to about 90 ppm based on the biodegradable polyester resincomposition according to an embodiment. The content of the siliconelement may range from about 1 ppm to about 80 ppm based on thebiodegradable polyester resin composition according to an embodiment.The content of the silicon element may range from about 1 ppm to about50 ppm based on the biodegradable polyester resin composition accordingto an embodiment.

In addition, the biodegradable polyester resin composition according toan embodiment may include a metal element. The metal element may bederived from the metal salt. The content of the metal element may rangefrom about 0.1 ppm to about 100 ppm based on the biodegradable polyesterresin composition according to an embodiment. The content of the metalelement may range from about 0.5 ppm to about 90 ppm based on thebiodegradable polyester resin composition according to an embodiment.The content of the metal element may range from about 1 ppm to about 80ppm based on the biodegradable polyester resin composition according toan embodiment. The content of the metal element may range from about 1ppm to about 50 ppm based on the biodegradable polyester resincomposition according to an embodiment.

In addition, the biodegradable polyester resin composition according toan embodiment may have surface tension, a water contact angle, adiiodomethane contact angle, surface free energy, dispersity andpolarity.

The surface tension, the water contact angle, the diiodomethane contactangle, the surface free energy, the dispersity and the polarity may bemeasured from the surface of the polyester sheet.

In the biodegradable polyester resin composition according to anembodiment, the surface tension may range from about 30 dynes to about55 dyne. In the biodegradable polyester resin composition according toan embodiment, the surface tension may range from about 35 dynes toabout 50 dyne.

In the biodegradable polyester resin composition according to anembodiment, the water contact angle may range from about 60° to about90°. In the biodegradable polyester resin composition according to anembodiment, the water contact angle may range from about 65° to about85°. In the biodegradable polyester resin composition according to anembodiment, the water contact angle may range from about 67° to about80°.

In the biodegradable polyester resin composition according to anembodiment, the diiodomethane contact angle may range from about 20° toabout 40°. In the biodegradable polyester resin composition according toan embodiment, the diiodomethane contact angle may range from about 20°to about 35°.

In the biodegradable polyester resin composition according to anembodiment, the surface free energy may range from about 40 mN/m toabout 60 mN/m. In the biodegradable polyester resin compositionaccording to an embodiment, the surface free energy may range from about42 mN/m to about 55 mN/m.

In the biodegradable polyester resin composition according to anembodiment, the dispersity may range from about 35 mN/m to about 55mN/m. In the biodegradable polyester resin composition according to anembodiment, the dispersity may range from about 40 mN/m to about 50mN/m.

In the biodegradable polyester resin composition according to anembodiment, the polarity may range from about 2 mN/m to about 8 mN/m. Inthe biodegradable polyester resin composition according to anembodiment, the polarity may range from about 3 mN/m to about 7 mN/m.

The surface tension, water contact angle, diiodomethane contact angle,surface free energy, dispersity and polarity of the biodegradablepolyester resin composition according to an embodiment may be within theabove ranges due to the composition of the biodegradable polyesterresin, the oligomer, the reinforcing material, the chain extender, themetal salt, the anti-hydrolysis agent and the heat stabilizer andprocesses such as the esterification, the polycondensation reaction, thechain extension reaction and the heat treatment reaction. Accordingly,the biodegradable polyester resin composition according to an embodimentmay have appropriate hydrolysis and appropriate biodegradability.

The above contents are described in more detail through the followingexamples. However, the following examples are only for illustrating thepresent disclosure, and the scope of the present disclosure is notlimited thereto.

Preparation Example

Preparation of Pretreated Cellulose Nanocrystals (CNC)

Dry powder-type cellulose nanocrystals (NVC-100, Manufacturer:Celluforce) having a particle size of about 1 μm to about 50 μm weredispersed in water at 1% by weight, and then sonicated at an output of20000 J/5 for 1 minute using a tip-type ultrasonic disperser, therebyproducing pretreated nanocellulose.

Monomer Composition for Preparing Oligomer

1,4-butanediol (1,4-BDO), terephthalic acid (TPA) and adipic acid (AA)were uniformly mixed in a molar ratio of about 3:1:2. Here, the averageparticle diameter of the terephthalic acid (TPA) was about 150 μm.

Preparation of Oligomer

1,4-butanediol (1,4-BDO), terephthalic acid (TPA) and adipic acid (AA)were uniformly mixed in a molar ratio of about 3:1:2. Here, the averageparticle diameter of the terephthalic acid (TPA) was about 130 μm. Next,the mixture was esterified at about 220° C. under normal pressure forabout 10 minutes, and the hydrolysis regulator was prepared.

Chain extender: Tri(4-isocyanatophenyl)methane

EXAMPLE Example 1

Preparation of Biodegradable Polyester Resin

First Operation: Pretreating to Obtain Slurry

As shown in Table 1, pretreated nanocellulose, 1,4-butanediol (1,4-BDO)and terephthalic acid (TPA) were mixed in a molar ratio (1,4-BDO:TPA) of1.2:1 and fed into a slurry tank (the bottom of the slurry tank was ananchor type, the height to an agitator was 40 mm, and three rotaryblades were provided) in a non-catalytic state. Here, D50 of theterephthalic acid (TPA) was 130 μm, and the standard deviation (SD) ofD50 of the terephthalic acid (TPA) was 30.

Next, the mixture was pretreated by stirring at 60° C. and 100 rpm for 1hour, and a slurry was obtained without phase separation.

Second Operation: Obtaining Prepolymer

The slurry obtained in the first step was fed into a reactor through asupply line, and tetrabutyl titanate (Dupont, Tyzor® TnBT product) as atitanium-based catalyst was fed at 250 ppm thereinto, followed byperforming a first esterification at 220° C. under normal pressure forabout 2 hours until 95% of by-product water was discharged.

53 mol % of 1,4-butanediol (1,4-BDO) based on the total number of molesof diol components, 53 mol % of adipic acid (AA) based on the totalnumber of moles of dicarboxylic acid, and 200 ppm of tetrabutyl titanate(Dupont, Tyzor® TnBT product) as a titanium-based catalyst based on thetotal weight of a diol, an aromatic dicarboxylic acid and an aliphaticdicarboxylic acid were added to the reaction product, and then secondesterification was performed at 210° C. under normal pressure for about2 hours 30 minutes until 95% of by-products was discharged. As a result,a second esterification product was produced.

Next, the monomer composition was added in a content ranging from about1 part by weight based on 100 parts by weight of the esterificationproduct to the second esterification product. A mixture of the monomercomposition and the second esterification product was subjected to thirdesterification at about 220° C. for about 20 minutes. Next, a prepolymerhaving a number average molecular weight of about 1200 g/mol wasprepared by the third esterification.

Third Operation: Polycondensing

400 ppm of tetrabutyl titanate (Dupont, Tyzor® TnBT product) as atitanium-based catalyst and 200 ppm of a triethylene phosphatestabilizer were added to the prepolymer and stabilized for about 10minutes. Next, the temperature of the reaction mixture was elevated to250° C., and then a polycondensation reaction was carried out at 0.5Torr for 4 hours, thereby preparing a polymer having a number averagemolecular weight of 55000 g/mol.

Next, about 0.5 wt % of tri(4-isocyanatophenyl)methane, based on theamount of the polymer, was added to the polymer. Next, the polymer wassubjected to a chain extension reaction at about 240° C. for about 10minutes. Next, the polymer was cooled at 5° C., and then cut, therebyobtaining a biodegradable polyester resin pellet.

Example 2

As shown in Tables 1 and 2 below, the contents of adipic acid,terephthalic acid, cellulose nanocrystals, a monomer composition and achain extender were varied. The polymer was cooled without a chainextension reaction, thereby obtaining a biodegradable polyester resinpellet. Next, the biodegradable polyester resin pellet was fed into atwin-screw extruder, melt-extruded at about 250° C. for about 2 minutes,and cooled at about 5° C., followed by cutting. As a result, a pelletwas produced again. Except for the contents and the process, otherprocesses were carried out in the substantially same manner as inExample 1.

Examples 3 to 6 and Comparative Examples 1 and 2

As shown in Tables 1 and 2, the contents of adipic acid, terephthalicacid, cellulose nanocrystals, a monomer composition and a chain extenderwere varied. Other processes, except for the contents and the process,were carried out in substantially the same manner as in Example 1 or 2.

Examples 7 to 13 and Comparative Example 3

The first esterification and the second esterification were carried out,but the third esterification was not carried out. In addition, theoligomer was added to the prepolymer in the polycondensation step toproduce a polymer. As shown in the following Tables 3 and 4, thecontents of adipic acid, terephthalic acid, cellulose nanocrystals, anoligomer and a chain extender and process conditions were varied. Otherprocesses were carried out in substantially the same manner as inExample 1 or 2.

Manufacture of Biodegradable Polyester Sheet

After preparing two Teflon sheets, a stainless steel (SUS) mold having asize 12 cm×12 cm was placed on one Teflon sheet, and about 7 g of theprepared polyester resin pellet was put into the stainless steel (SUS)mold having a size 12 cm×12 cm. Next, the mold was covered with anotherTeflon™ sheet, and placed in the center of a hot press (manufacturer:Widlab, model name: WL 1600SA) having a surface size of about 25 cm×25cm. The mold was maintained at about 210° C. under a pressure of about10 Mpa for about 3 minutes, and then detached, followed by immediatelycooling in water of 20° C. for about 30 seconds. Next, a biodegradablepolyester sheet having an area of about 10 cm×10 cm and a thickness ofabout 300 μm was manufactured.

Manufacture of Biodegradable Polyester Film

After drying the biodegradable polyester resin pellet at 80° C. for 5hours, melt extrusion was carried out at 160° C. using Blown FilmExtrusion Line (Manufacturer: YOOJIN ENGINEERING), thereby manufacturinga biodegradable polyester film having a thickness of 50 μm.

TABLE 1 Monomer 1,4- composition Chain Chain Re- BDO TPA AA CNC (partsby extender extension extrusion Classification (mol %) (mol %) (mol %)(ppm) weight) (wt %) reaction process Example 1 120 47 53 700 1 0.5 ◯ XExample 2 120 50 50 3 X ◯ Example 3 120 53 47 700 2 0.5 ◯ X Example 4120 45 55 3 0.5 ◯ X Example 5 120 55 45 700 2 0.1 ◯ X Example 6 120 5050 700 2 X ◯ Comparative 120 60 40 Example 1 Comparative 120 50 50 7 ◯ ◯Example 2

As shown in Table 2 below, the molar ratio of the monomer compositionand the conditions of the third esterification were varied.

TABLE 2 Third 1,4-BDO TPA AA Third esterification Classifi- (molar(molar (molar esterification temperature cation ratio) ratio) ratio)time (min) (° C.) Example 1 3 1 2 20 220 Example 2 3.5 1.5 2 20 210Example 3 4 1 3 25 210 Example 4 3 1 2 30 220 Example 5 2 1 1 15 220Example 6 2.5 1 1.5 15 210 Comparative Example 1 Comparative Example 2

TABLE 3 1,4- Chain Chain Heat BDO TPA AA CNC Oligomer extender extensiontreatment Classification (mol %) (mol %) (mol %) (ppm) (wt %) (wt %)reaction process Example 7 140 47 53 5 0.5 ◯ X Example 8 140 51.5 48.5 X◯ Example 9 140 48 52 700 2 0.5 ◯ X Example 10 140 45 55 2 0.5 ◯ XExample 11 140 50 50 700 3 0.1 ◯ X Example 12 140 50 50 700 X ◯Comparative 120 51.5 48.5 Example 3

TABLE 4 First Second esterifi- First esterifi- Second cation esterifi-cation esterifi- Classifi- temperature cation temperature cationPretreat- cation (° C.) time (° C. time ment Example 7 220 1.5 240 1.5 ◯Example 8 225 1.5 225 2.0 ◯ Example 9 220 2.0 225 2.0 ◯ Example 10 2152.0 230 2.0 ◯ Example 11 220 1.5 220 2.5 ◯ Example 12 220 1.5 220 2.0 ◯Comparative 200 2.0 205 2.0 X Example 3

Evaluation Examples

Evaluation Example 1: An Average Particle Diameter (D50) and a StandardDeviation

<Average Particle Diameter (D50) and Standard Deviation of AromaticDicarboxylic Acid>

With regard to a particle size distribution (PSD), the average particlediameter (D50) and standard deviation (SD) of an aromatic dicarboxylicacid (TPA or DMT) were obtained using a particle size analyzer MicrotracS3500 (Microtrac Inc) according to the following conditions:

Use Environment

-   -   Temperature: 10 to 35° C., humidity: 90% RH, non-condensing        maximum    -   D50 and SD, which are average particle size distributions for        each section, were measured.

The standard deviation means the square root of the variance and may becalculated using the software.

<Particle Diameter of Nanocellulose>

The particle size and average particle deviation of nanocellulose weremeasured using the principle of dynamic light scattering (DLS) at 25° C.and a measurement angle of 175° using Zetasizer Nano ZS (Manufacturer:Marven). Here, a peak value derived through the polydispersity index(PdI) in a confidence interval of 0.5 was measured as a particlediameter.

Evaluation Example 2: Hydrolysis Degree

The biodegradable polyester resins prepared in the examples and thecomparative examples were immersed in 80° C. water (100% RH), and thenan accelerated hydrolysis test was carried out.

Specifically, 5 g of each of the polyester resins of the examples andthe comparative examples was added to 500 mL of deionized water (DIWater), and then blocked with a stopper to prevent water fromevaporating and subjected to an accelerated hydrolysis test in an 80° C.convection (hot air) oven. The humidity environment of the biodegradablepolyester sheet is the same as that at 100% RH because it is created byimmersion in water.

The number average molecular weights of the polyester resins of theexamples and the comparative examples after a certain period weremeasured using gel permeation chromatography (GPC). A hydrolysis degreewas derived by dividing a difference between the initial number averagemolecular weight and the number average molecular weight after a certainperiod by the initial number average molecular weight.

Evaluation Example 3: Biodegradability

Each of the biodegradable polyester resins prepared in the examples andthe comparative examples was mixed with the following compost, and wassubjected to a biodegradation acceleration test at 60° C. and a relativehumidity of 90%.

The number average molecular weight of each of the polyester resins ofthe examples and the comparative examples was measured using gelpermeation chromatography (GPC) after a certain period. Biodegradabilitywas derived by dividing the difference between the initial numberaverage molecular weight and the number average molecular weight after acertain period by the initial number average molecular weight.

Compost

Manufacturer: Taeheung F&G

Product Name: Jisaengto (by-product fertilizer grade 1 compost)

Compost components: 40 wt % of pig manure, 15 wt % of chicken manure, 37wt % of sawdust, 5 wt % of zeolite, a microbial agent 3 wt %

Evaluation Example 4: Oligomer Content

The biodegradable polyester pellet manufactured in each of the examplesand the comparative examples was pulverized to obtain a biodegradablepolyester powder having an average particle diameter (D50) of about 50μm. The biodegradable polyester powder was immersed in acetonitrile forabout 24 hours. Next, a supernatant was sampled, and the molecularweights and contents of the components extracted by LC mass weremeasured using dibutyl phthalate as a standard.

HR-LC-MS equipment: Model name (Orbitrap HR LC-MS, Q-Exactive,manufactured by Thermo Fisher)

Column: C18

LC detector: 254 nm

Eluent: 5% ACN (with 0.1% Formic acid)/95% H₂O-->100% ACN (with 0.1%Formic acid)

Ionization mode: ESI mode

Mass: Positive 50-750, 500-3000

Evaluation Example 5: Water contact angle and polarity

The water contact angle and polarity of the surface of each of thebiodegradable polyester sheet manufactured in the examples and thecomparative examples were measured under the following conditions:

Surface tension: Wet tension test mixtures Nos. 40 to 64

Manufacturer: Wako

Components: ethylene glycol, monoethyl ether

Surface energy meter: MSA One-Click SFE (product name)/KRUSS(manufacturer)

Biodegradability was measured as shown in Tables 5 and 6 below.

TABLE 5 Molecular Molecular Molecular Molecular Molecular Molecularweight weight weight weight weight weight reduction reduction reductionreduction reduction reduction rate after rate after rate after rateafter rate after rate after one week two weeks three weeks four weekssix weeks nine weeks Classification (%) (%) (%) (%) (%) (%) Example 1 5262 71 78 87 90 Example 2 53 64 71 78 88 90 Example 3 57 64 71 78 88 91Example 4 51 63 70 78 87 90 Example 5 56 65 72 77 86 90 Example 6 58 6573 78 87 90 Comparative 38 59 66 73 80 82 Example 1 Comparative 48 61 6572 77 79 Example 3

TABLE 6 Molecular Molecular Molecular Molecular Molecular Molecularweight weight weight weight weight weight reduction reduction reductionreduction reduction reduction rate after rate after rate after rateafter rate after rate after one week two weeks three weeks four weekssix weeks nine weeks Classification (%) (%) (%) (%) (%) (%) Example 7 5565 72 78 87 90 Example 8 61 66 71 78 88 90 Example 9 54 64 71 78 88 90Example 10 57 67 71 78 87 90 Example 11 56 66 71 78 87 90 Example 12 5966 71 78 87 90 Comparative 74 79 84 86 91 92 Example 3

As shown in Tables 7 and 8 below, hydrolysis degrees were measured.

TABLE 7 Molecular Molecular Molecular Molecular Molecular Molecularweight weight weight weight weight weight reduction reduction reductionreduction reduction reduction rate after rate after rate after rateafter rate after rate after one week two weeks three weeks four weekssix weeks nine weeks Classification (%) (%) (%) (%) (%) (%) Example 1 5287 94 95 97 97 Example 2 52 89 95 96 97 97 Example 3 58 91 95 96 97 97Example 4 47 87 94 95 96 97 Example 5 55 88 95 96 97 97 Example 6 57 8995 96 97 97 Comparative 31 89 93 95 96 96 Example 1 Comparative 45 88 9395 96 96 Example 2

TABLE 8 Molecular Molecular Molecular Molecular Molecular Molecularweight weight weight weight weight weight reduction reduction reductionreduction reduction reduction rate after rate after rate after rateafter rate after rate after one week two weeks three weeks four weekssix weeks nine weeks Classification (%) (%) (%) (%) (%) (%) Example 7 5589 95 96 97 97 Example 8 47 86 94 96 97 97 Example 9 49 88 95 96 97 97Example 10 58 89 95 96 97 97 Example 11 55 88 95 96 97 97 Example 12 5489 94 96 97 97 high Comparative 81 94 96 97 97 97 Example 3

As shown in Tables 9 and 10 below, the contents of the first oligomer,the second oligomer, the third oligomer and the fourth oligomer weremeasured.

TABLE 9 First Second Third Fourth Total Classifi- oligomer oligomeroligomer oligomer oligomers cation (ppm) (ppm) (ppm) (ppm) (ppm) Example1 3681 2835 1222 1535 10238 Example 2 4133 3216 1559 1890 11654 Example3 3293 2853 979 1256 9835 Example 4 4163 2959 1421 1785 12035 Example 53249 2546 1623 1678 11021 Example 6 3523 2842 1489 1553 10456Comparative 1650 752 652 653 4250 Example 1 Comparative 1582 523 541 6013965 Example 2

TABLE 10 First Second Third Fourth Total Classifi- oligomer oligomeroligomer oligomer oligomers cation (ppm) (ppm) (ppm) (ppm) (ppm) Example1 4163 2959 1451 1768 11354 Example 2 1582 523 546 606 3645 Example 33293 2853 979 1256 9351 Example 4 3249 2546 1623 1679 10214 Example 53856 2756 1538 1589 10900 Example 6 1625 678 635 758 4205 Comparative3150 2765 895 1534 9856 example

First oligomer molecular weight: 421.18

Second oligomer molecular weight: 623.3

Third oligomer molecular weight: 643.3

Fourth oligomer molecular weight: 843.4

As shown in Tables 11 and 12 below, the surface properties of thebiodegradable polyester sheets according to the examples and thecomparative examples were measured.

TABLE 11 Water Surface Surface contact Diiodomethane free tension anglecontact angle energy Dispersity Polarity Classification (dyne) (°) (°)(mN/m) (mN/m) (mN/m) Example 1 42 73.71 33.2 47.6 42.7 4.7 Example 2 4271.15 25.44 51.33 45.99 5.4 Example 3 41 72.16 26.66 50.3 44.6 5.4Example 4 42 73.46 27.3 51.2 43.5 5.6 Example 5 41 70.59 24.33 51.1 44.65.3 Example 6 40 74.15 30.8 49.5 42.1 5.4 Comparative 39 67.5 25.5 45.340.3 4.31 Example 1 Comparative 41 69.5 24.3 45.3 40.5 4.18 Example 2

TABLE 12 Water Surface Surface contact Diiodomethane free tension anglecontact angle energy Dispersity Polarity Classification (dyne) (°) (°)(mN/m) (mN/m) (mN/m) Example 1 42 73.7 33.2 47.6 42.7 4.7 Example 2 4271.5 25.4 51.33 45.99 5.4 Example 3 41 72.6 26.6 50.3 44.6 5.4 Example 442 73.4 27.3 51.2 43.5 5.6 Example 5 41 70.5 24.3 51.1 44.6 5.3 Example6 40 74.1 30.8 49.5 42.1 5.4 Comparative 39 77.5 27.5 49.3 43.3 5.31Example 1 Comparative 41 75.5 29.3 51.3 43.5 5.18 Example 2

As shown in Tables 5 to 12, the biodegradable resin compositionsaccording to the examples may have appropriate hydrolysis, appropriatebiodegradability and appropriate surface properties.

A biodegradable polyester resin composition according to an embodimentincludes a hydrophilic regulator having a molecular weight of about 400to about 1300. In addition, the hydrophilic regulator can adjust thehydrophilicity and/or hydrophobicity of the biodegradable polyesterresin composition according to an embodiment. Accordingly, thehydrophilic regulator can control the hydrolysis degree of thebiodegradable polyester resin composition according to an embodiment.

Due to the hydrophilic regulator, a preparation process, or the like,the biodegradable polyester resin composition according to an embodimentcan have appropriate hydrolysis and appropriate biodegradability.

In particular, the biodegradable polyester resin composition accordingto an embodiment has a low initial hydrolysis degree and a high laterhydrolysis degree. In addition, the biodegradable polyester resincomposition according to an embodiment can have appropriatebiodegradability per hydrolysis.

Accordingly, the biodegradable polyester resin composition according toan embodiment can be efficiently applied to a film for packaging and thelike. That is, a film made of the biodegradable polyester resincomposition according to an embodiment can be used for general purposessuch as packaging. Here, since the biodegradable polyester resincomposition according to an embodiment has a low initial hydrolysisdegree, the biodegradable polyester film can maintain mechanical andchemical properties to a certain extent or more within a period ofnormal use by a user.

In addition, since the biodegradable polyester resin compositionaccording to an embodiment has a high later hydrolysis degree, a filmmade of the biodegradable polyester resin composition according to anembodiment can be degraded when discarded after use. In particular,since the biodegradable polyester resin composition according to anembodiment has a high later hydrolysis, decomposition by ambientmoisture and decomposition by microorganisms in the biodegradablepolyester resin composition according to an embodiment can becomplemented each other. Accordingly, the biodegradable polyester resincomposition according to an embodiment can have a high biodegradabilitydegree while having a low initial hydrolysis degree.

In addition, the biodegradable polyester resin composition according toan embodiment can have a biodegradability per aliphatic carboxylic acidof 1.5 or more. That is, the biodegradable polyester resin compositionaccording to an embodiment has a high biodegradability degree whilehaving a low aliphatic carboxylic acid content.

Accordingly, since the biodegradable polyester resin compositionaccording to an embodiment includes aromatic carboxylic acid in arelatively high content, it can have a high biodegradability degree in alater period while having a high hydrolysis resistance degree in aninitial period.

The biodegradable polyester resin composition according to an embodimentcan maintain mechanical and chemical properties above a certain levelduring the period of use by a user. At the same time, since thebiodegradable polyester resin composition according to an embodiment hasa high later hydrolysis degree, it can be degraded in rivers or sea.That is, the biodegradable polyester resin composition according to anembodiment can solve environmental problems such as marine plasticproblems.

Although the preferred embodiments of the present disclosure have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the disclosureas disclosed in the accompanying claims.

DESCRIPTION OF SYMBOLS

-   -   slurry stirrer 100    -   esterification part 200    -   polycondensation reaction part 300    -   post-treatment part 400    -   first recovery part 510    -   second recovery part 520

What is claimed is:
 1. A biodegradable polyester resin composition,comprising: a polyester resin comprising a diol, an aromaticdicarboxylic acid and an aliphatic dicarboxylic acid; and a hydrophilicregulator, wherein a content of the hydrophilic regulator ranges from5000 ppm to 20000 ppm based on a total amount of the biodegradablepolyester resin composition, and wherein the hydrophilic regulator has amolecular weight of 400 to
 1300. 2. The biodegradable polyester resincomposition according to claim 1, wherein the hydrophilic regulatorcomprises an oligomer formed by reaction of at least two of the diol,the aromatic dicarboxylic acid and the aliphatic dicarboxylic acid. 3.The biodegradable polyester resin composition according to claim 1,wherein a hydrolysis degree after one week is 35% to 60%, and ahydrolysis degree after three weeks is 85% or more, wherein thehydrolysis degree after one week and the hydrolysis degree after threeweeks are measured by a measurement method below: wherein in themeasurement method, the hydrolysis degree after one week is a numberaverage molecular weight reduction rate, compared to an initial numberaverage molecular weight of the biodegradable polyester film, of thebiodegradable polyester film placed for one week under high-temperatureand high-humidity conditions of 80° C. and a relative humidity of 100%,and the hydrolysis degree after three weeks is a number averagemolecular weight reduction rate, compared to an initial number averagemolecular weight of the biodegradable polyester film, of thebiodegradable polyester film placed for three weeks underhigh-temperature and high-humidity conditions of 80° C. and a relativehumidity of 100%.
 4. The biodegradable polyester resin compositionaccording to claim 1, wherein the hydrophilic regulator comprises: afirst oligomer having a molecular weight ranging from 415 to 425; asecond oligomer having a molecular weight ranging from 620 to 630; athird oligomer having a molecular weight ranging from 640 to 650; and afourth oligomer having a molecular weight ranging from 840 to
 850. 5.The biodegradable polyester resin composition according to claim 4wherein a content of the first oligomer ranges from 3000 to 5000 ppmbased on the polyester resin, a content of the second oligomer rangingfrom 2000 ppm to 4000 ppm based on the biodegradable polyester polyesterresin, a content of the third oligomer ranging from 500 ppm to 2000 ppmbased on the biodegradable polyester polyester resin, and a content ofthe fourth oligomer ranging from 700 ppm to 2500p ppm based on thebiodegradable polyester polyester resin.
 6. The biodegradable polyesterresin composition according to claim 1, wherein the hydrophilicregulator comprises a first oligomer, wherein the first oligomercomprises one first unit represented by Formula 6 below and one secondunit represented by Formula 7 below:


7. The biodegradable polyester resin composition according to claim 6wherein the hydrophilic regulator comprises a second oligomer; and athird oligomer, wherein the second oligomer comprises one first unitdenoted above and two second units denoted above, the third oligomercomprises two first units denoted above and one second unit denotedabove, and the second oligomer is comprised in the hydrophilic regulatorin a higher content than the third oligomer.
 8. The biodegradablepolyester resin composition according to claim 7 wherein the hydrophilicregulator further comprises a fourth oligomer, wherein the fourtholigomer comprises two first units denoted above and two second unitsdenoted above.
 9. The biodegradable polyester resin compositionaccording to claim 1, wherein a water contact angle of the biodegradablepolyester resin composition measured by a measurement method below is65° to 90°, and a polarity of the biodegradable polyester resincomposition measured by a measurement method below is 4 mN/m to 7 mN/m:wherein in the measurement method the biodegradable polyester resincomposition is dried at 80° C., placed in a stainless steel mold, andcompressed at 210° C. under a pressure of 10 MPa for 3 minutes toproduce a polyester sheet having a thickness of 300 μm, and the watercontact angle and the polarity are measured on a surface of thepolyester sheet.
 10. The biodegradable polyester resin compositionaccording to claim 1, wherein a biodegradability of the biodegradablepolyester resin composition after one week is 45% to 65%, abiodegradability of the biodegradable polyester resin composition afternine weeks is 85% or more, wherein the biodegradability after one weekand the biodegradability after nine weeks are measured by a measurementmethod below: wherein in the measurement method the biodegradabilityafter one week is a molecular weight reduction rate, compared to aninitial molecular weight of the biodegradable polyester resincomposition, of the biodegradable polyester resin composition placed at60° C. and a relative humidity of 90% for one week under compostingconditions, and the biodegradability after nine weeks is a molecularweight reduction rate, compared to an initial molecular weight of thebiodegradable polyester resin composition, of the biodegradablepolyester resin composition placed at 60° C. and a relative humidity of90% for nine weeks under composting conditions.
 11. A biodegradablepolyester resin composition, comprising a polyester resin comprising adiol, an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid,a hydrolysis degree after one week is 35% to 60%, and a hydrolysisdegree after three weeks is 85% or more, wherein the hydrolysis degreeafter one week and the hydrolysis degree after three weeks are measuredby a measurement method below: wherein in the measurement method thehydrolysis degree after one week is a number average molecular weightreduction rate, compared to an initial number average molecular weightof the biodegradable polyester resin composition, of the biodegradablepolyester resin composition placed for one week under high-temperatureand high-humidity conditions of 80° C. and a relative humidity of 100%,and the hydrolysis degree after three weeks is a number averagemolecular weight reduction rate, compared to an initial number averagemolecular weight of the biodegradable polyester resin composition, ofthe biodegradable polyester resin composition placed for three weeksunder high-temperature and high-humidity conditions of 80° C. and arelative humidity of 100%.
 12. The biodegradable polyester resincomposition according to claim 11, wherein a biodegradability after nineweeks is 85% or more, wherein the biodegradability after nine weeks is amolecular weight reduction rate, compared to an initial molecular weightof the biodegradable polyester resin composition, of the biodegradablepolyester resin composition placed at 60° C. and a relative humidity of90% for nine weeks under composting conditions.
 13. The biodegradablepolyester resin composition according to claim 11, wherein abiodegradability after one week is 45% to 75%, wherein thebiodegradability after one week is a molecular weight reduction rate,compared to an initial molecular weight of the biodegradable polyesterresin composition, of the biodegradable polyester resin compositionplaced at 60° C. and a relative humidity of 90% for one week undercomposting conditions.
 14. The biodegradable polyester resin compositionaccording to claim 11, wherein a hydrolysis degree after two weeks is80% to 95%, wherein the hydrolysis degree after two weeks is a numberaverage molecular weight reduction rate, compared to an initial numberaverage molecular weight of the biodegradable polyester resincomposition, of the biodegradable polyester resin composition placed fortwo weeks under high-temperature and high-humidity conditions of 80° C.and a relative humidity of 100%.
 15. The biodegradable polyester resincomposition according to claim 14, wherein a hydrolysis degree afterfour weeks is 85% or more, wherein the hydrolysis degree after fourweeks is a number average molecular weight reduction rate, compared toan initial number average molecular weight of the biodegradablepolyester resin composition, of the biodegradable polyester resincomposition placed for four weeks under high-temperature andhigh-humidity conditions of 80° C. and a relative humidity of 100%, anda hydrolysis degree increase rate from one week to two weeks is 29%/weekto 50%/week, and a hydrolysis degree increase rate from three weeks tofour weeks is 0.01%/week to 3%/week.
 16. The biodegradable polyesterresin composition according to claim 13, wherein a biodegradabilityafter four weeks is 73% to 85%, wherein the biodegradability after fourweeks is a number average molecular weight reduction rate, compared toan initial number average molecular weight of the biodegradablepolyester resin composition, of the biodegradable polyester resincomposition placed for four weeks under high-temperature andhigh-humidity conditions of 80° C. and a relative humidity of 100%, anda biodegradability increase rate from one week to four weeks is3.5%/week to 8%/week.
 17. The biodegradable polyester resin compositionaccording to claim 11, wherein an acid value of the biodegradablepolyester resin composition is 2.0 mg KOH/g or less.
 18. Thebiodegradable polyester resin composition according to claim 17, whereinan oligomer having a molecular weight ranging from 400 to 1300 iscomprised in an amount ranging from 5000 ppm to 20000 ppm based on atotal amount of the biodegradable polyester resin composition.
 19. Thebiodegradable polyester resin composition according to claim 18, whereinthe oligomer comprises the diol, the aromatic dicarboxylic acid and thealiphatic dicarboxylic acid.
 20. A biodegradable molded article,comprising a biodegradable resin composition, wherein the biodegradableresin composition comprises a polyester resin comprising a diol, anaromatic dicarboxylic acid and an aliphatic dicarboxylic acid; and ahydrophilic regulator, wherein a content of the hydrophilic regularranges from 5000 ppm to 20000 ppm based on a total amount of thebiodegradable polyester resin composition, and wherein the hydrophilicregulator has a molecular weight of 400 to 1300.